Cold cathode x-ray tube and method of manufacture

Abstract

The application belongs to the technical field of X-ray generating device, and relates to a cold cathode X-ray tube and a preparation method thereof. The cold cathode X-ray tube comprises a shell and a cathode assembly, a grid assembly, a beam current ring and an anode assembly arranged in sequence. The cathode assembly has a cathode cover covering a carbon nanotube emission layer, and a low work function material is deposited on the surface of the emission layer; the grid assembly adopts a photoetching metal mesh as a grid layer and is isolated from the cathode through an insulating layer; the beam current ring is used as a ring electrode for actively regulating the shape and landing point of the electron beam; and the anode assembly comprises a tungsten target with a specific inclination angle. The components are connected and fixed through vacuum brazing, and a fixing groove supports 360-degree adjustable installation. The preparation method comprises the steps of cathode emission layer processing, grid cutting and assembly, anode brazing, shell welding and general assembly. Through optimization of the cathode emission performance, the grid control precision and the active focusing of the beam current, the application realizes efficient regulation and control of the electron beam and stability and adjustability of the X-ray output.

Description

Technical Field

[0001] This invention relates to the field of X-ray generating device technology, specifically to a cold cathode X-ray tube and its preparation method. Background Technology

[0002] Currently, X-ray tubes are mainly divided into two categories: hot cathode and cold cathode. Approximately 95% of X-ray tubes on the market use a hot cathode structure. Its working principle is based on thermionic emission: the cathode filament (usually tungsten) emits electrons after being heated by an electric current. These electrons are accelerated in the high-voltage electric field between the anode and cathode, ultimately striking the anode target (such as tungsten, molybdenum, or rhodium) to produce X-rays. The basic structure of a hot cathode X-ray tube includes a cathode, an anode target, a tube shell, and a high-voltage power supply.

[0003] In contrast, cold cathode X-ray tubes account for approximately 5% of the market. Their core difference lies in the electron emission method: cold cathodes employ field emission (cold electron emission) instead of thermionic emission, achieving electron emission without heating the cathode. This results in potential advantages such as low energy consumption, fast response, and long lifespan. However, existing cold cathode X-ray tubes still face challenges in structural design, manufacturing processes, and performance stability. In particular, the complex cathode-gate structure, difficult fabrication process, and high cost, coupled with insufficient precision in electron beam focusing and landing point control, limit their application in small-volume, high-precision X-ray equipment.

[0004] Furthermore, traditional cold cathode X-ray tubes still have shortcomings in terms of electron beam control, structural compactness, and installation flexibility, making it difficult to meet the needs of modern portable, multi-angle beam output X-ray imaging and detection. Therefore, there is an urgent need for a cold cathode X-ray tube with a simplified structure, feasible manufacturing process, stable performance, and active electron beam control capability, as well as its fabrication method. Summary of the Invention

[0005] The present invention aims to provide a cold cathode X-ray tube and its preparation method. The X-ray tube has the characteristics of compact structure, precise electron beam control, and stable and reliable beam output, and is suitable for various X-ray application scenarios such as medical treatment and industrial inspection.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a cold cathode X-ray tube, comprising: a cathode assembly, a gate assembly, a beam ring, an anode assembly, a housing, and a mounting groove. The cathode assembly, gate assembly, beam ring, and anode assembly are disposed inside the housing. The cathode assembly includes a cathode pillar, a carbon nanotube emitting layer disposed on the cathode pillar, and a cathode cover covering the outer side of the carbon nanotube emitting layer. The anode assembly includes an anode cover, an anode target disposed within the anode cover, and an anode pillar connected to the anode target. The gate assembly includes a gate layer and an insulating layer; the gate layer is a photolithographic metal mesh with a microporous structure, and the insulating layer is disposed between the cathode assembly and the gate layer. The beam ring is disposed between the cathode assembly and the anode assembly and is used to control the shape and landing point of the electron beam. In use, the cathode assembly emits electrons, which, after being controlled by the gate and focused by the beam ring, strike the anode target to generate X-rays.

[0008] In addition to the above-mentioned technical features, the present invention has also made optimizations and improvements in the following aspects: As a preferred technical solution of the present invention, the carbon nanotube emission layer is carbon nanotube paper, on which a work function material layer is deposited. The work function of the work function material layer is less than 5.0 eV, and the material composition of the work function material layer includes at least one of strontium oxide, calcium oxide, magnesium oxide, aluminum oxide or barium oxide.

[0009] As a preferred embodiment of the present invention, the gate layer is a photolithographic nickel mesh with a aperture of 15 μm, an open area ratio of more than 50%, and a thickness of 25 μm; the insulating layer is polyimide or mica sheet with a thickness of 100 μm, and the insulating layer and the gate layer are formed by laser cutting, and the edge of the work function material layer is provided with alignment holes.

[0010] As a preferred embodiment of the present invention, the beam ring is a ring electrode, which achieves active focusing and deflection of the electron beam through external voltage control, and is used to adjust the size, shape and landing position of the electron beam on the anode target.

[0011] As a preferred embodiment of the present invention, the cathode column includes a substrate and a conductive column. The substrate is a square copper sheet, and the conductive column is a copper column arranged coaxially. The carbon nanotube emission layer is fixed to the center of the substrate by conductive adhesive.

[0012] As a preferred embodiment of the present invention, the anode target is a tungsten target, the anode target is provided with a slope, the inclination angle of the slope is matched with the beam exit angle and the focal point size, the anode target is connected to the anode substrate by a molybdenum sheet and fixed by vacuum brazing.

[0013] In a preferred embodiment of the present invention, the outer shell, beam ring, anode cover, and cathode cover are connected by vacuum brazing, with a brazing temperature of 800°C and a vacuum degree of 10. -5 Pa.

[0014] As a preferred embodiment of the present invention, the fixing groove is an adjustable angle mounting groove to match the X-ray tube exiting the beam at any angle within a 360° range.

[0015] Secondly, the present invention also provides a method for preparing a cold cathode X-ray tube, comprising the following steps:

[0016] S1. Preparation of cathode assembly: Carbon nanotube paper is cut into shape, cleaned with deionized water, treated with inert gas at high temperature, and then vacuum-deposited with low work function material to obtain carbon nanotube emission layer, which is then fixed to the cathode column substrate with conductive adhesive.

[0017] S2. Fabrication of gate assembly: The photolithographic nickel mesh and insulating layer are laser-cut into shape respectively, and then assembled with the cathode assembly by insulating bolts;

[0018] S3. Preparation of anode assembly: After assembling the tungsten target, molybdenum sheet and anode substrate, vacuum braze them;

[0019] S4. Assemble the outer shell and beam ring: Vacuum braze the outer shell section and the beam ring to form the main outer shell;

[0020] S5. Final assembly: The cathode assembly, grid assembly, beam ring, and anode assembly are sequentially installed into the main body shell and vacuum brazed and sealed in sections.

[0021] S6. Seal and fix the slot to complete the fabrication of the cold cathode X-ray tube.

[0022] As a preferred technical solution of the present invention, the inert atmosphere high-temperature treatment in step S1 includes: heating to 500°C at 10°C / min and holding for 1 hour under argon gas, and then heating to 1200°C at 20°C / min and holding for 2 hours; during the vacuum evaporation process, the carbon nanotube paper rotates and revolves at 20 rpm / min, the evaporation current is 100A, and the deposition time is 20 min.

[0023] This invention, by systematically integrating a cathode assembly, a gate assembly, a beam ring, and an anode assembly with specific structures, can produce the following significant advantages compared to existing technologies:

[0024] 1. A high-efficiency, stable, and long-life field emission system

[0025] This application precisely isolates and assembles the cathode emission layer of "carbon nanotube paper with low work function material deposited on its surface" and the gate layer of "photolithographic nickel mesh with specific pore size and high porosity" through "a 100μm thick polyimide / mica insulating layer with alignment holes formed by laser cutting".

[0026] Through the above technical solution, the low work function layer significantly reduces the electron emission barrier of carbon nanotubes, while the high porosity microporous gate enables efficient and uniform extraction of emitted electrons at extremely close range with a lower extraction voltage. Furthermore, the insulating layer not only ensures reliable electrical isolation, but its precise laser cutting and alignment hole design ensure accurate alignment between the cathode emitting surface and the gate micropores, thereby avoiding localized electric field concentration. This results in a lower initiation voltage, higher emission current density, and significantly enhanced stability for field emission. The overall lifespan of the emission system far exceeds the expected effect of simply stacking individual components.

[0027] 2. Dynamically adjustable, high-precision electron beam shaping and focusing

[0028] This application introduces a ring-shaped electrode beam ring located between the cathode and anode, independently controllable by an external voltage, based on the initial electron beam generated by the aforementioned cathode-gate assembly. The gate extracts and initially shapes the electron beam, while the beam ring performs "fine-tuning" on this basis. By coordinating the adjustment of the gate voltage and the beam ring voltage, two-stage active and dynamic control of the electron beam's shape, size, and landing point is achieved. This composite control mechanism of "gate pre-focusing + beam ring active deflection / focusing" enables the electron beam to form a smaller, more regularly shaped, and more precisely positioned focal point on the anode target. Furthermore, its adjustment response speed and flexibility far exceed those of traditional designs using only a single electrostatic lens, ensuring the acquisition of a high-quality, programmable X-ray beam.

[0029] 3. Compact, highly reliable integrated vacuum sealing structure

[0030] This application specifies that all metal components, including the cathode cover, anode cover, beam ring, and outer casing, are manufactured using a process involving 800℃ and 10℃. -5 The X-ray tube is connected using vacuum brazing under Pa conditions, combined with a 360° adjustable fixing groove. This unified ultra-high vacuum brazing process not only achieves permanent, leak-free sealing of all interfaces, ensuring the long-term stability of the ultra-high vacuum environment inside the tube, but also creates an integrated structure with extremely high mechanical strength and thermal stability. The combination of this integrated structure and the adjustable fixing groove allows the X-ray tube to be miniaturized while withstanding the mechanical stress of installation at any angle and maintaining consistent beam output performance. The degree of combination of structural compactness and environmental adaptability is unattainable by step-by-step welding or mechanical sealing methods.

[0031] 4. Optimized thermal management and beam output performance

[0032] This application uses a tungsten target with a specific tilt angle as the anode, and connects it to the anode substrate through a molybdenum sheet, which is also fixed by vacuum brazing.

[0033] The bevel angle of the anode target is precisely matched with the electron beam incident angle and the required exit angle, maximizing the effective output and directionality of X-rays. A molybdenum sheet, acting as a transition layer with matching thermal expansion coefficients, forms a high-strength, high-thermal-conductivity connection with the tungsten target and copper anode substrate after vacuum brazing. This design efficiently conducts the high heat generated by electron bombardment to the anode substrate and external heat dissipation system, significantly reducing the target surface operating temperature and slowing target ablation. This, in turn, improves power tolerance and beam stability while further extending tube life. Such synergistic optimization of thermal, structural, and optical performance is difficult to achieve simply by replacing the target material or improving the heat dissipation method.

[0034] 5. Highly repeatable and scalable preparation process:

[0035] In the preparation method, this application forms a complete process chain from the "inert gas high-temperature treatment" and "low work function material vacuum evaporation" of the cathode emitting layer, to the "laser cutting and forming" of each component, and then to the multi-stage "vacuum brazing and sealing".

[0036] The process parameters for each step are not set in isolation, but are optimized and matched to the material properties after the preceding steps. Specifically, the high-temperature treatment of the cathode removes impurities, providing a clean substrate for subsequent vapor deposition and ensuring high-quality adhesion of the low work function layer; while the precision laser cutting of each component provides perfect assembly clearance and consistency for subsequent vacuum brazing. This deep integration of the process chain guarantees a high degree of consistency and repeatability in the final product performance.

[0037] In summary, through deep integration and collaborative design, this invention enables key performance indicators such as cathode emission characteristics, grid control capability, beam ring focusing function, vacuum sealing reliability, and heat dissipation efficiency to mutually promote and enhance each other, resulting in an unexpected and significant technical effect where the overall performance far exceeds the sum of the performance of each part. It features high performance, high reliability, miniaturization, and good fabrication capabilities. Attached Figure Description

[0038] Figure 1 This is a cross-sectional view of the cold cathode X-ray tube of the present invention;

[0039] Figure 2 This is a cross-sectional view of the substrate, cathode assembly, and gate assembly assembled according to the present invention;

[0040] Figure 3 This is a cross-sectional schematic diagram of the cathode-gate assembly of the present invention.

[0041] Figure label:

[0042] 10. Cathode assembly; 11. Cathode column; 111. Substrate; 112. Conductive column; 12. Carbon nanotube emission layer; 13. Cathode cover; 20. Grid assembly; 21. Grid layer; 22. Insulating layer; 30. Beam ring; 40. Anode assembly; 41. Anode cover; 42. Anode target; 43. Anode column; 44. Molybdenum sheet; 45. Anode substrate; 50. Outer shell; 60. Fixing groove. Detailed Implementation

[0043] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0044] I. Explanation of descriptive terms used in this invention

[0045] The embodiments provided in conjunction with the technical solutions of this invention are intended to make the invention more thorough and complete, and to fully express the scope of the invention to those skilled in the art. It should be noted that unless otherwise specifically stated in this invention, the relative arrangements of components described in these embodiments should be interpreted as merely exemplary and not as a limitation on the technical solutions of this invention.

[0046] In this invention, when directional terms such as "up," "down," "left," "right," "bottom," and "top" are used, they are defined relative to the directions shown in the accompanying drawings and are used only to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly. These or other directional terms should not be construed as restrictive terms.

[0047] In this invention, the terms "a," "an," "an," "the," and similar words used do not indicate quantity limitations and can represent singular or plural. The terms "comprising," "including," "having," and any variations thereof used in this invention are intended to cover non-exclusive inclusion; the terms "first," "second," "third," etc., used in this invention are merely to distinguish similar objects and do not represent a specific ordering of objects.

[0048] In this invention, when a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device. When a specific device is described as being connected to other devices, the specific device may be directly connected to the other devices without an intermediary device, or it may be not directly connected to the other devices but have an intermediary device.

[0049] Furthermore, this invention does not discuss in detail the technologies and equipment known to those skilled in the art, but where appropriate, such technologies and equipment should be considered part of the specification.

[0050] II. The core technical problem to be solved by the technical solution of this application

[0051] In current X-ray tube technology, the hot cathode type dominates the market, but it relies on heated filaments to emit electrons, resulting in high energy consumption and limited response speed. While the cold cathode type uses field emission, requires no preheating, and has the potential for low energy consumption, fast response, and long lifespan, it still faces significant challenges in practical applications: its cathode-gate structure design is complex, requiring sophisticated manufacturing processes, leading to high costs; insufficient precision in electron beam focusing and landing point control affects the stability and accuracy of X-ray output; and its overall structure is not compact enough, resulting in poor installation flexibility and difficulty in adapting to the needs of portable, multi-angle beam-emission modern detection equipment. Therefore, current cold cathode X-ray tubes face bottlenecks in technological maturity, performance stability, and structural simplification, limiting their widespread adoption in small-volume, high-precision applications.

[0052] III. Based on the above problems, the present invention specifically provides a technical solution to solve the above problems, which is described below in conjunction with the appendix. Figures 1-3 The technical solutions of the present invention will be described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the scope of protection of the present invention.

[0053] Example 1

[0054] like Figures 1 to 3 As shown, this embodiment provides a cold cathode X-ray tube and its preparation method.

[0055] The cold cathode X-ray tube includes: a cathode assembly 10, a grid assembly 20, a beam ring 30, an anode assembly 40, a housing 50, and a mounting groove 60. All internal components are encapsulated within the housing 50.

[0056] The cathode assembly 10 includes a cathode post 11, a carbon nanotube emitting layer 12 disposed on the cathode post 11, and a cathode cover 13 covering the outside of the carbon nanotube emitting layer 12. The cathode post 11 is integrally formed from a substrate 111 (a square copper sheet with a side length of 21 mm and a thickness of 5 mm) and a conductive post 112 (a coaxially arranged copper post with an outer diameter of 10 mm and a wall thickness of 1 mm). The carbon nanotube emitting layer 12 is a square carbon nanotube paper with a side length of 2 cm, which is fixed to the center of the substrate 111 with conductive adhesive.

[0057] The gate assembly 20 is disposed in front of the electron emission direction of the cathode assembly 10, and includes a gate layer 21 and an insulating layer 22. The gate layer 21 is a photolithographic nickel mesh, laser-cut into a square sheet with a side length of 21 mm, a hole diameter of 15 μm, an open area ratio of more than 50%, a thickness of 25 μm, and tiny alignment holes at the four corners. The insulating layer 22 is a polyimide film, also laser-cut into a square sheet with a side length of 21 mm and a thickness of 100 μm, with a circular hole of 6 mm radius in the center and alignment holes at the four corners corresponding to the gate layer 21. The insulating layer 22 is placed between the carbon nanotube emission layer 12 and the gate layer 21 of the cathode assembly 10, and the three (gate layer 21, insulating layer 22, and cathode post substrate 111) are pressed and fixed by insulating bolts, maintaining a precise 100 μm spacing between the gate layer 21 and the carbon nanotube emission layer 12.

[0058] The beam ring 30 is a copper ring electrode that is fixed to the inner wall of the housing 50 by vacuum brazing and is located in the electron beam path between the gate assembly 20 and the anode assembly 40.

[0059] The anode assembly 40 includes an anode cover 41, an anode target 42 disposed within the anode cover 41, and an anode post 43 connected to the anode target 42. The anode target 42 is a tungsten target, machined into a beveled shape with a specific angle. The anode target 42 is connected to a copper anode substrate 45 via a 3mm thick molybdenum sheet 44. The anode cover 41 and the anode target 42 (including the molybdenum sheet 44 and the anode substrate 45) are integrally formed by vacuum brazing.

[0060] The outer casing 50 is a segmented metal structure, and the various parts (including the beam ring 30, anode cover 41, and cathode cover 13) are all vacuum brazed at 800℃ and 10℃. -5 A high-vacuum cavity is formed by sealing the connection under the condition of Pa.

[0061] The mounting slot 60 is installed on the outside of the housing 50 and is an adjustable-angle mechanical mounting slot that allows the entire X-ray tube to rotate and lock within a 360° range.

[0062] 2. Preparation method of cold cathode X-ray tube

[0063] The cold cathode X-ray tube of this embodiment is prepared according to the following steps:

[0064] S1. Preparation of cathode assembly:

[0065] a) Cut the carbon nanotube paper into square pieces with a side length of 2cm.

[0066] b) After cleaning with deionized water and drying, place in a tube furnace and heat to 500°C at 10°C / min under argon gas and hold for 1 hour, then heat to 1200°C at 20°C / min and hold for 2 hours, then cool naturally.

[0067] c) Place the treated carbon nanotube paper and a low work function material (in this embodiment, a mixture of strontium oxide and barium oxide) into a vacuum coating chamber, and evacuate to 10 °C. -5 Pa.

[0068] d) Heat the chamber to 200°C, slowly increase the evaporation current to 100A, keep the carbon nanotube paper 30cm away from the evaporation source, and make it rotate and revolve at a speed of 20rpm / min at the same time. Deposit for 20 minutes to form a carbon nanotube emission layer 12 with a surface deposited active function material layer (active function <5.0eV).

[0069] e) The prepared carbon nanotube emission layer 12 is attached to the center of the cathode column substrate 111 using conductive adhesive.

[0070] S2. Fabrication of the gate assembly: The photolithographic nickel mesh and polyimide film are laser-cut into 21mm side-length rectangular pieces with alignment holes. The gate layer 21, the insulating layer 22 and the cathode post substrate 111 with the carbon nanotube emission layer 12 attached are aligned and pressed together using insulating bolts.

[0071] S3. Preparation of the anode assembly: Assemble the tungsten target (anode target 42) with the beveled surface, the molybdenum sheet 44, and the anode substrate 45, place them in a vacuum brazing furnace, and use AgCu brazing filler metal to braze at 800℃ for 10 minutes. -3 Vacuum brazing was performed under Pa conditions.

[0072] S4. Assemble the outer shell and beam ring: After cleaning the two sections of the outer shell 50 and the copper beam ring 30, fix them with clamps and braze them in a vacuum brazing furnace at 800℃ for 10 minutes. -5 Brazing under Pa conditions forms the main body shell with a current ring 30.

[0073] S5. Final Assembly: The anode assembly 40, beam ring 30 (already integrated with the housing), and grid assembly 20 (already assembled with the cathode assembly 10) are sequentially placed into their respective positions on the main housing 50. Vacuum brazing and sealing are performed in steps: First, the anode cover 41 is brazed to the main housing; then, the cathode cover 13 is brazed to the main housing; finally, the conductive lead-out portion of the grid is brazed to the insulating ceramic seal. All brazing steps are performed at 800℃ for 10 minutes. -5 The process is carried out under strict process windows of Pa, using appropriate matching solders (such as silver-copper eutectic solder for copper-copper, and titanium-based solder for copper-ceramic).

[0074] S6. Encapsulation and fixing groove: Install the adjustable angle fixing groove 60 onto the outer shell 50 to complete the fabrication of the entire X-ray tube.

[0075] During operation, a high voltage (tube voltage) is applied between the cathode assembly 10 and the anode assembly 40. Because the carbon nanotube emission layer 12 is coated with a low work function material, a strong electric field is generated even under the relatively low voltage between the cathode and the gate layer 21, inducing field emission from the carbon nanotubes and producing an electron beam. The electron beam first passes through the gate layer 21, which has a precise microporous structure, undergoing initial extraction and shaping. Subsequently, the electron beam enters the electrostatic field region formed by the beam ring 30. By independently adjusting the voltage applied to the beam ring 30, the electron beam can be actively focused and deflected, precisely controlling its size, shape, and final impact point (i.e., focal point) on the inclined surface of the anode target 42. The accelerated high-energy electrons bombard the tungsten target, generating X-rays, which are then directionally emitted through the inclined surface of the anode target for subsequent use.

[0076] The implementation of this embodiment has achieved the following unexpected technical effects:

[0077] Highly efficient and stable cold emission: The synergy between the low work function layer and the high aperture ratio microgate enables low-voltage start-up, high current density and uniform and stable field emission with a very short spacing set by the precision insulating layer, and significantly extends the lifetime.

[0078] Precise composite control of the electron beam: The deep integration of the two-level control mechanism of "gate extraction and shaping" and "beam ring active focusing / deflection" enables unprecedented precision and flexibility in the control of the focal point size, shape and position, far exceeding the effect of a single electrostatic lens.

[0079] Highly reliable integrated design: All metal components are integrated using a unified ultra-high vacuum brazing process, ensuring ultimate vacuum sealing and mechanical strength. Combined with a mounting slot that can be installed at any angle, this design achieves a 50% reduction in size while ensuring reliability for use at all angles.

[0080] Excellent heat dissipation and beam output performance: The combination of tungsten target bevel design, molybdenum sheet transition layer and overall brazing process optimizes the heat conduction path and stress distribution, significantly improving the power tolerance of the anode and beam output stability.

[0081] High process repeatability: From material processing (such as CNT high-temperature purification), precision machining (laser cutting alignment) to multi-step vacuum brazing, the process parameters of each link are deeply matched, ensuring the high consistency of product performance and the feasibility of large-scale production.

[0082] Example 2

[0083] The main difference between this embodiment and Embodiment 1 lies in the work function material composition of the carbon nanotube emitter layer, the gate insulating layer material, and some parameters of the anode target connection method.

[0084] Work function material layer: In this embodiment, barium oxide (BaO) is used as a low work function material for vacuum evaporation, and the evaporation process parameters are the same as in Example 1.

[0085] Insulation layer: In this embodiment, a 100μm thick natural mica sheet is used instead of a polyimide film. It is formed using the same laser cutting process.

[0086] Anode target connection: In this embodiment, the thickness of the molybdenum sheet is adjusted to 2mm, the vacuum brazing temperature is adjusted to 780℃, and other conditions remain unchanged.

[0087] Using barium oxide as a single material may result in more uniform film adhesion under certain process conditions. Mica sheets offer higher high-temperature resistance and insulation strength, potentially providing more stable insulation under long-term high-power operation. Adjusting the molybdenum sheet thickness and brazing temperature optimizes for specific thermal expansion matching requirements, aiming to further reduce thermal stress at the joint. This embodiment achieves similar high performance to Embodiment 1, and may have a slight advantage in high-temperature stability.

[0088] Example 3

[0089] The main difference between this embodiment and Embodiment 1 lies in the structural form of the beam ring.

[0090] In this embodiment, the beam ring is not a simple single-ring structure (it could also be a single-ring structure, which would have a beam effect but not optimal controllability), but rather consists of two coaxial copper rings that can be independently voltaged (a double-ring structure), with a 2mm gap between the two rings. By controlling the voltage of the two rings separately, a more complex composite electric field can be formed to achieve more complex electron beam shaping, such as forming a ring-shaped or specific asymmetric focal point.

[0091] The dual-ring beam ring structure provides more degrees of freedom for electric field modulation, enabling more complex and precise control of electron beam spatial distribution. It is particularly suitable for applications with special shape requirements for X-ray focal points (such as linear focal points at specific angles, micro-focal point arrays, etc.), further expanding the applicability and imaging / detection capabilities of X-ray tubes.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0093] Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them; when the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

Claims

1. A cold cathode X-ray tube, characterized in that, include: The system comprises a cathode assembly, a gate assembly, a beam ring, an anode assembly, a housing, and a mounting groove; the cathode assembly, gate assembly, and anode assembly are disposed inside the housing. The beam ring is disposed between the cathode assembly and the anode-cathode assembly and is welded to the outer shell; the outer diameter of the beam ring is the same as the outer diameter of the outer shell, and the inner diameter of the beam ring is the same as the diameter of the cathode assembly. The cathode assembly includes a cathode column, a carbon nanotube emission layer disposed on the cathode column, and a cathode cover covering the outside of the carbon nanotube emission layer. The carbon nanotube emission layer is carbon nanotube paper with a work function material layer deposited on its surface. The work function of the work function material layer is less than 5.0 eV. The anode assembly includes an anode cover, an anode target disposed inside the anode cover, and an anode column connected to the anode target; The gate assembly includes a gate layer and an insulating layer. The gate layer is a photolithographic metal mesh with a microporous structure, and the insulating layer is disposed between the cathode assembly and the gate layer. The gate layer is a photolithographic nickel mesh with a pore size of 15 μm, an open area ratio of more than 50%, and a thickness of 25 μm. The insulating layer is polyimide or mica sheet with a thickness of 100 μm. The beam ring is disposed between the cathode assembly and the anode assembly. The beam ring is a ring electrode that actively focuses and deflects the electron beam through external voltage control, and is used to adjust the size, shape and landing position of the electron beam on the anode target. In use, the cathode assembly emits electrons, which are then focused by the grid and beam ring before striking the anode target to generate X-rays.

2. The cold cathode X-ray tube according to claim 1, characterized in that, The material composition of the work function material layer includes at least one of strontium oxide, calcium oxide, magnesium oxide, aluminum oxide, or barium oxide.

3. The cold cathode X-ray tube according to claim 1, characterized in that, The insulating layer and the gate layer are formed by laser cutting, and the edge of the work function material layer is provided with alignment holes.

4. The cold cathode X-ray tube according to claim 1, characterized in that, The cathode post includes a substrate and a conductive post. The substrate is a square copper sheet, and the conductive post is a copper post arranged coaxially. The carbon nanotube emission layer is fixed to the center of the substrate by conductive adhesive.

5. The cold cathode X-ray tube according to claim 1, characterized in that, The anode target is a tungsten target with a beveled surface. The angle of the beveled surface matches the beam exit angle and the focal spot size. The anode target is connected to the anode substrate by a molybdenum sheet and fixed by vacuum brazing.

6. The cold cathode X-ray tube according to claim 1, characterized in that, The outer shell, beam ring, anode cover, and cathode cover are connected by vacuum brazing at a temperature of 800°C and a vacuum degree of 10. -5 Pa.

7. The cold cathode X-ray tube according to claim 1, characterized in that, The fixing slot is an adjustable angle mounting slot to match the X-ray tube's beam exit at any angle within a 360° range.

8. A method for preparing a cold cathode X-ray tube, characterized in that, Includes the following steps: S1. Preparation of cathode assembly: Carbon nanotube paper is cut into shape, cleaned with deionized water, treated with high temperature in an inert atmosphere, and then vacuum-deposited with low work function materials to obtain carbon nanotube emission layer, which is then fixed to the cathode column substrate with conductive adhesive. S2. Fabrication of gate assembly: The photolithographic nickel mesh and insulating layer are laser-cut into shape respectively, and then assembled with the cathode assembly by insulating bolts; S3. Preparation of anode assembly: After assembling the tungsten target, molybdenum sheet and anode substrate, vacuum braze them; S4. Assemble the outer shell and beam ring: Vacuum braze the outer shell section and the beam ring to form the main outer shell; S5. Final assembly: The cathode assembly, grid assembly, beam ring, and anode assembly are sequentially installed into the main body shell and vacuum brazed and sealed in sections. S6. Seal and fix the slot to complete the fabrication of the cold cathode X-ray tube.

9. The preparation method according to claim 8, characterized in that, The inert atmosphere high-temperature treatment in step S1 includes: heating to 500°C at 10°C / min and holding for 1 hour under argon gas, then heating to 1200°C at 20°C / min and holding for 2 hours; during the vacuum evaporation process, the carbon nanotube paper rotates on its own axis and revolves around the sun at 20 rpm / min, the evaporation current is 100A, and the deposition time is 20 min.

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