A high-power X-ray source and its vacuum external circulation liquid target assembly

Abstract

The present invention discloses a high-power X-ray source and its vacuum-external circulating liquid target assembly. The vacuum-external circulating liquid target assembly comprises an electron window and a liquid metal target. After the electron beam passes through the electron window, it strikes the liquid metal target, generating X-rays. The liquid metal target circulates, removing heat deposited by the electron beam and cooling the target. By employing a technique in which the electron beam, after passing through the window, strikes the circulating liquid target outside of a vacuum, the present invention significantly increases the power of the X-ray source and addresses the issues of damage to a fixed target and the inability of in-tube spray-type liquid targets to be used in conventional sealed X-ray sources.

Description

Technical Field

[0001] The present invention belongs to the technical field of X-ray sources, and in particular relates to a high-power X-ray source and a vacuum external circulation liquid target assembly thereof. Background Art

[0002] X-ray sources are widely used in industrial inspection, scientific instrumentation, medical imaging, and treatment. In an X-ray source, an electron beam bombards a target material to produce X-rays. Most of the electron beam power is ultimately deposited in the target as heat. Excessive beam power can melt the target, so thermal management of X-ray conversion targets is a core technology for X-ray sources.

[0003] In a transmission-type X-ray source, diamond or beryllium is usually used as a transmission window. A thin film of a high atomic number metal such as tungsten is deposited on the vacuum side of the diamond or beryllium. The electron beam bombards the tungsten film to generate X-rays. In X-ray imaging applications, the X-ray focal spot needs to be relatively small. To avoid damage to the transmission window or target due to heat, the power of the transmission X-ray tube is usually very low, generally below 10W. Fixed transmission targets used for transmission X-ray tubes, such as Figure 1 shown.

[0004] Reflective X-ray sources generally use copper (or copper alloy) as the substrate of the tungsten target. The heat is transferred to the outer shell through the target material and the substrate, and is removed by air cooling or liquid cooling. Figure 2 As shown in the figure. For reflection X-ray sources, the target typically has a reflection angle, which can reduce the electron beam power density by an order of magnitude while achieving a small focal spot. Because the heat dissipation conditions of a reflection target are better than those of a transmission target, the target temperature rise is generally smaller than that of a transmission target. However, when the electron beam power is further increased, the target temperature becomes too high and thermal stress increases. This can cause cracking of the target layer or melting of the copper heat sink. Furthermore, the excessive metal vapor pressure at high temperatures can lead to a decrease in the vacuum level within the tube and contamination of the insulating component surface, causing insulation failure or cathode damage under high voltage.

[0005] Whether it is a transmission target or a reflection target, further increasing the power generally requires the use of rotating target technology, which can effectively reduce the power density. However, the use of a rotating target requires a large target disk, which greatly increases the size of the X-ray tube. In addition, the rotating target must have a motor and power supply to drive the bearing rotor, further increasing the size and weight of the X-ray tube assembly. Figure 3 shown.

[0006] In order to solve the above difficulties, circulating liquid can be used as X-ray conversion target. At present, there are methods that use liquid targets in X-ray sources, such as Figure 4As shown, in this method, a nozzle is used to spray a liquid metal target in the vacuum chamber of the X-ray source. After the metal liquid is bombarded by electrons and produces X-rays, it is recovered by a recoverer. By using a jet-type liquid target in the vacuum chamber, the energy of the electron beam can be very low, thereby generating low-energy, high-dose X-rays. However, this liquid target is used directly in a vacuum environment and is heated by the electron beam, which affects the vacuum degree and high-voltage insulation. Generally, a vacuum pump is required to continuously evacuate the vacuum. Due to its relatively complex structure and large equipment size, this liquid target method is suitable for X-ray sources used in scientific research instruments and cannot be used in applications where ordinary sealed X-ray sources are used. Summary of the Invention

[0007] In order to solve the problems that existing fixed targets cannot be applied to compact high-power X-ray sources and that in-tube spray-type liquid targets cannot be applied to compact sealed X-ray sources, the present invention provides a vacuum external circulation liquid target assembly that can be applied to high-power X-ray sources. The liquid target can take away and cool the heat deposited by the electron beam, thereby increasing the power of the X-ray source.

[0008] The present invention is achieved through the following technical solutions:

[0009] A vacuum external circulation liquid target assembly, comprising an electron window and a liquid metal target;

[0010] After passing through the electron window, the electron beam bombards the liquid metal target to generate X-rays;

[0011] The liquid metal target takes away the heat of electron beam deposition through circulation flow and is cooled.

[0012] The present invention adopts the technology of bombarding a circulating liquid target outside a vacuum after the electron beam passes through a window, which greatly improves the power of the X-ray source and solves the problems that a fixed target may be damaged and that the in-tube spray-type liquid target cannot be applied to an ordinary sealed X-ray source.

[0013] As a preferred embodiment, the electronic window of the present invention is made of beryllium, diamond, copper or titanium.

[0014] As a preferred embodiment, the thickness of the electronic window of the present invention is between 10 micrometers and 0.3 millimeters.

[0015] As a preferred embodiment, the liquid target assembly of the present invention is suitable for electron energy of 300kV-25MV.

[0016] As a preferred embodiment, the metal liquid target of the present invention adopts a lead-based alloy material with a high atomic number and a low melting point.

[0017] As a preferred embodiment, the present invention modifies the surface of the electron window in contact with the liquid metal target. By modifying the surface of the electron window, the present invention improves the wettability between the electron window and the liquid metal target, thereby enhancing the cooling effect of the liquid metal target on the electron window.

[0018] As a preferred embodiment, the circulation flow speed of the liquid metal target of the present invention is 0.1-2 m / s.

[0019] In a second aspect, the present invention provides a high-power X-ray source, including the vacuum external circulation liquid target assembly of the present invention;

[0020] The vacuum external circulation liquid target assembly is used to convert electrons emitted by the cathode assembly into X-rays, and to take away the heat deposited by the electron beam and perform cooling.

[0021] As a preferred embodiment, the X-ray source of the present invention further comprises an accelerator;

[0022] Accelerators include but are not limited to electrostatic accelerators or radio frequency accelerators;

[0023] The acceleration device is used to accelerate the electrons emitted by the cathode assembly so that the electrons have enough energy to penetrate the electron window and bombard the liquid target.

[0024] As a preferred embodiment, the X-ray source of the present invention outputs X-rays in a transmission or reflection manner.

[0025] The present invention has the following advantages and beneficial effects:

[0026] Under the same power density conditions, the vacuum external circulation liquid target assembly of the present invention can greatly reduce the target area temperature, thereby greatly improving the use power of the sealed X-ray source without a rotating target. At the same time, the X-ray source has a very small volume and is suitable for various application occasions of current ordinary sealed X-ray sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0028] Figure 1 This is a diagram of the working principle of a traditional fixed transmission target.

[0029] Figure 2 This is a diagram of the working principle of a traditional fixed reflective target.

[0030] Figure 3 This is the working principle diagram of the traditional transmission type fixed rotating target.

[0031] Figure 4This is a diagram of the working principle of a traditional jet liquid target.

[0032] Figure 5 This is a working principle diagram of the vacuum external circulation liquid (transmission) target assembly according to the first embodiment of the present invention.

[0033] Figure 6 To adopt Figure 5 The X-ray source using vacuum external circulation liquid target technology is shown.

[0034] Figure 7 This is a working principle diagram of the vacuum external circulation liquid (reflection) target assembly according to the second embodiment of the present invention.

[0035] Figure 8 To adopt Figure 7 The X-ray source using vacuum external circulation liquid target technology is shown.

[0036] Figure 9 This is a radio frequency accelerating tube X-ray source (transmission type) based on vacuum external circulation liquid target technology according to the third embodiment of the present invention.

[0037] Markings and corresponding parts names in the accompanying drawings:

[0038] 1-electron beam, 2-window, 3-window holder, 4-X-ray, 5-liquid metal target, 6-liquid metal target circulation pipe, 7-target substrate, 8-cathode core column, 9-cathode, 10-cathode cover, 11-insulating tube shell, 12-anode cover, 13-cooling flange, 14-liquid target assembly, 15-sealed Kovar, 16-accelerating chamber. DETAILED DESCRIPTION

[0039] Hereinafter, the terms "include" or "may include" used in various embodiments of the present invention indicate the presence of the invented function, operation or element, and do not limit the addition of one or more functions, operations or elements. In addition, as used in various embodiments of the present invention, the terms "include", "have" and their cognates are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing, and should not be understood as excluding the presence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing or the possibility of adding one or more features, numbers, steps, operations, elements, components or combinations of the foregoing.

[0040] In various embodiments of the present invention, the expression "or" or "at least one of A or / and B" includes any or all combinations of the words listed simultaneously. For example, the expression "A or B" or "at least one of A or / and B" may include A, may include B, or may include both A and B.

[0041] The expressions (such as "first", "second", etc.) used in the various embodiments of the present invention may modify the various constituent elements in the various embodiments, but may not limit the corresponding constituent elements. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only used to distinguish one element from other elements. For example, a first user device and a second user device indicate different user devices, although both are user devices. For example, without departing from the scope of the various embodiments of the present invention, a first element may be referred to as a second element, and similarly, a second element may also be referred to as a first element.

[0042] It should be noted that when a component is described as being “connected” to another component, the first component may be directly connected to the second component, and a third component may be “connected” between the first and second components. Conversely, when a component is described as being “directly connected” to another component, it can be understood that there is no third component between the first and second components.

[0043] The terms used in various embodiments of the present invention are only used to describe the purpose of specific embodiments and are not intended to limit the various embodiments of the present invention. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. Unless otherwise limited, all terms used here (including technical terms and scientific terms) have the same meaning as those of ordinary skill in the art generally understood by the various embodiments of the present invention. The terms (such as those defined in generally used dictionaries) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having idealized meaning or too formal meaning, unless clearly defined in various embodiments of the present invention.

[0044] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0045] Example 1

[0046] When the power of the X-ray source is further increased, the traditional fixed target will fail due to the high temperature of the target; and the jet-type liquid target X-ray source has a complex structure and a large device volume, which is not suitable for ordinary sealed X-ray sources. To address the above problems, this embodiment provides a vacuum external circulation liquid target assembly (transmission type) based on an electron transmission window. Its principle is as follows: Figure 5As shown, a thin window 2 made of a low atomic mass, high thermal conductivity material separates the vacuum within the tube from the liquid metal target 5. This ensures that the vacuum level and high-voltage insulation performance of the X-ray tube are not affected by the vapor pressure of the liquid metal target material. After penetrating window 2, the electron beam 1 strikes the circulating liquid metal target 5, generating X-rays. The X-rays then penetrate window 2 and are used for imaging and other applications. The majority of the electron beam power is deposited in the liquid metal target. Driven by a circulating pump, the high-temperature liquid metal target 5 circulates in a pipe 6 and is cooled by heat exchange.

[0047] To balance optimal heat dissipation and X-ray extraction efficiency, the vacuum external circulation liquid metal target assembly based on the electron transmission window in this embodiment is generally suitable for electron energies of no less than 300kV (300kV-25MV). The higher the electron energy, the greater the technical advantages of the vacuum external liquid circulation target. Because window 2 has a certain thickness, if the electron beam energy is too low, most of the electron power will be deposited in window 2. Window 2 has a low atomic number, which reduces the X-ray conversion efficiency.

[0048] In order to reduce the loss of electron energy, in this embodiment, the electron transmission window 2 uses a thin film of a material with good thermal conductivity and low equivalent atomic number, such as beryllium, diamond window, copper and titanium; the thickness of the window 2 is between 10 microns and 0.3 mm.

[0049] The material of the liquid metal target 5 of this embodiment is but not limited to gallium-indium-lead alloy or other lead-based alloy materials with high atomic number and low melting point.

[0050] In this embodiment, the surface of the side of the window 2 that contacts the liquid metal target 5 is modified to improve the wettability between the window 2 and the liquid metal target 5 and enhance the cooling effect of the liquid metal target 5 on the window 2 .

[0051] The thickness design of the liquid metal target 5 in this embodiment is related to the equivalent energy of the electron beam 1 after penetrating the window 2 , and the circulation flow speed of the liquid metal target 5 is 0.1-2 m / s.

[0052] This embodiment applies the above-mentioned vacuum outer circulation liquid target assembly based on the electron transmission window to the X-ray source. Its specific structure is as follows: Figure 6 As shown, the X-ray source primarily consists of a cathode assembly, an anode assembly, and a housing. The cathode assembly, including accessories such as the cathode core 8, cathode 9, and cathode cover 10, is used to emit electrons and provide grid control and focusing. The anode assembly, including accessories such as the anode cover 12, liquid target assembly 14, and cooling flange 13, is used to convert electrons into X-rays and remove deposited heat. The housing primarily includes accessories such as the insulating housing 11 and the sealing kovar 15, providing high-voltage insulation and support.

[0053] The working principle of this X-ray source is:

[0054] A high voltage is applied between the cathode assembly and the anode head, setting the cathode head at a relatively negative potential. This creates an electric field within the tube that accelerates and focuses electrons. The cathode emits electrons, which, under the influence of the electric field, fly toward the anode assembly. After penetrating the window, they strike the liquid metal target, generating X-rays through a process called bremsstrahlung. The X-rays are emitted from the tube and used for imaging. Most of the power of the electron beam is deposited on the liquid metal target. The majority of the heat from the target is directly removed by the circulating liquid and cooled by a heat exchanger. A portion of the heat is transferred to a cooling flange and cooled by water or air.

[0055] Example 2

[0056] In order to further improve the power consumption of the liquid target assembly of the above embodiment 1, this embodiment proposes a reflective vacuum external circulation liquid target assembly, the principle of which is as follows: Figure 7 As shown in the figure, a thin window 2 made of a low atomic mass and high thermal conductivity material separates the vacuum within the tube from the liquid metal target 5. This ensures that the vacuum level and high-voltage insulation performance of the X-ray tube are not affected by the vapor pressure of the liquid metal target material. After penetrating the window 2, the electron beam 1 strikes the circulating liquid metal target 5, generating X-rays. The X-rays are then reflected and passed through the window 2 for use in imaging and other applications. The majority of the electron beam power is deposited in the liquid metal target. Driven by a circulating pump, the high-temperature liquid metal target 5 circulates within the target substrate 7 and is cooled by heat exchange.

[0057] This embodiment applies the above-mentioned reflective vacuum external circulation liquid target assembly to an X-ray source. The specific structure of the X-ray source is as follows: Figure 8 The operating principle of the X-ray source is the same as that of the X-ray source of the first embodiment. The only difference is that the electron beam of the first embodiment passes through the window, bombards the liquid metal target, and then transmits through the window for output. The electron beam of the present embodiment passes through the window, bombards the liquid metal target to generate X-rays, and then the X-rays are reflected and output through the window. The rest of the operating process is the same and will not be described in detail here.

[0058] Example 3

[0059] In order to further increase the energy of the electron beam, this embodiment proposes a radio frequency accelerating tube type X-ray source based on the vacuum external circulation liquid target assembly of the above embodiment.

[0060] This embodiment takes the transmission type vacuum external circulation liquid target assembly as an example to explain in detail. Figure 9As shown, the accelerated X-ray source is mainly composed of an accelerating tube assembly and an anode assembly. The accelerating tube assembly includes a cathode assembly and an accelerating cavity, which is used to emit and accelerate electrons; the anode assembly is composed of a liquid target assembly 14 and a cooling flange 13, which is used to convert electrons into X-rays and take away the deposited heat. The X-ray source of this embodiment differs from the X-ray source of the above-mentioned embodiment 1 only in that this embodiment uses a radio frequency accelerating tube instead of the electrostatic accelerating tube commonly used in small X-ray tubes to accelerate the electrons generated by the cathode assembly. The other working principles are basically the same as those of the X-ray source of the above-mentioned embodiment 1 and will not be repeated here.

[0061] Example 4

[0062] In order to verify the technical effect of the vacuum external circulation liquid target assembly proposed in the above embodiment, this embodiment conducts simulation tests on the temperature changes of the vacuum external circulation liquid target assembly of the present invention and the traditional fixed target assembly at different powers under the same power density conditions. The specific process is as follows:

[0063] Using diamond as the window material, after injecting electron beam powers of 10W, 100W, and 1000W for 1 second into a target with a diameter of 1mm and a thickness of 1mm, the temperature rise under two conditions, using a solid target and a circulating liquid target assembly (liquid target flow rate of 1m / s), is simulated as shown in Table 1 below:

[0064] Table 1

[0065]

[0066] According to the simulation results shown in the table above:

[0067] After the liquid target of the present invention is used to replace the transmission solid target, the target temperature rise is reduced to 10.1% and 3.7% of the original value respectively (the temperature rise is reduced from 237 degrees to 24 degrees at 10W power, and the temperature rise is reduced from 1527 degrees to 57 degrees at 100W power);

[0068] After the liquid target of the present invention is used to replace the reflective solid target, the target temperature rise is reduced to 80%, 47.1% and 34.8% of the original value respectively (the temperature rise is reduced from 30 degrees to 24 degrees at 10W power, the temperature rise is reduced from 121 degrees to 57 degrees at 100W power, and the temperature rise is reduced from 1027 degrees to 357 degrees at 1000W power);

[0069] Simulations show that the higher the power, the more obvious the reduction in temperature rise is when the vacuum external circulation liquid target assembly of the present invention is used compared to traditional solid reflection and transmission targets.

[0070] Therefore, using vacuum external circulation liquid target technology instead of traditional fixed transmission and reflection targets can significantly reduce the maximum temperature of the target area. This temperature reduction further improves the non-uniform distribution of thermal stress in the target area. At the same time, the reliability of the electron transmission window is greatly improved under the cooling of the liquid target.

[0071] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A vacuum external circulation liquid target assembly, characterized in that: Includes electron window and liquid metal target; After passing through the electron window, the electron beam bombards the liquid metal target to generate X-rays; The liquid metal target takes away the heat deposited by the electron beam through a circulating flow and is cooled; The power of the electron beam is deposited in the liquid metal target. Part of the heat of the liquid metal target is directly taken away by the circulating liquid and then cooled by the heat exchange device. Part of the heat is transferred to the cooling flange and cooled by water cooling or air cooling. The surface of the electron window in contact with the liquid metal target is modified to improve the wettability between the electron window and the liquid metal target and enhance the cooling effect of the liquid metal target on the electron window.

2. The vacuum external circulation liquid target assembly according to claim 1, characterized in that: The electronic window is made of beryllium, diamond, copper or titanium.

3. The vacuum external circulation liquid target assembly according to claim 1, characterized in that: The thickness of the electronic window is between 10 micrometers and 0.3 millimeters.

4. The vacuum external circulation liquid target assembly according to claim 1, characterized in that: The liquid target assembly is suitable for electron energy of 300kV-25MV.

5. The vacuum external circulation liquid target assembly according to claim 3, characterized in that: The liquid metal target is made of a lead-based alloy material with a high atomic number and a low melting point.

6. A vacuum external circulation liquid target assembly according to any one of claims 1 to 5, characterized in that: The circulation flow speed of the liquid metal target is 0.1-2 m / s.

7. A high-power X-ray source, characterized in that: comprising the vacuum external circulation liquid target assembly according to any one of claims 1 to 6; The vacuum external circulation liquid target assembly is used to convert electrons emitted by the cathode assembly into X-rays, and to take away the heat deposited by the electron beam and perform cooling.

8. The high-power X-ray source according to claim 7, characterized in that: Also includes an acceleration device; The acceleration device is used to accelerate the electrons emitted by the cathode assembly; The acceleration device includes a radio frequency acceleration device or an electrostatic acceleration device.

9. The high-power X-ray source according to claim 8, characterized in that: The X-ray source outputs X-rays in a transmission or reflection manner.

Images