An external rotating target assembly, X-ray source and method based on phase change cooling

Abstract

The present invention discloses an external rotating target assembly, X-ray source, and method based on phase change cooling. The rotating target assembly includes a target cavity, a rotating target, a bearing, a drive coil, an atomizer, and an exhaust pipe. The target cavity is provided with a bearing and a drive coil on one side and an atomizer on the other side. The bottom of the target cavity is connected to the exhaust pipe. The rotating target is mounted in the target cavity via the bearing and is driven by the drive coil to achieve high-speed rotation. When an external electron beam bombards the rotating target, it generates X-rays, most of which are deposited on the rotating target as heat. The present invention uses a phase change cooling method. The atomizer continuously sprays liquid mist onto the rotating target. When the high-temperature position rotates to the position corresponding to the atomizer, the liquid mist droplets encounter the high-temperature rotating target and rapidly evaporate into high-temperature gas. The high-temperature gas is then extracted through the exhaust pipe, thereby cooling the rotating target. The present invention does not affect the quality and dose of the electron beam and X-rays.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear technology equipment application, and in particular to an external rotating target assembly based on phase change cooling, an X-ray source and a method. 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 the transmission window, and a high atomic number metal film such as tungsten is coated on the vacuum side of the diamond. In X-ray imaging applications, the X-ray focal spot needs to be relatively small. In order 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. The fixed transmission target used for the transmission X-ray tube is as follows: Figure 1 shown.

[0004] To further increase the power, it is generally necessary to use rotating target technology. Rotating targets can effectively reduce the power density, thereby providing the feasibility of increasing the average power of the beam at a small beam spot size.

[0005] Since the electron beam in the accelerator is generated, accelerated and transmitted in a vacuum, the electron beam usually bombards the rotating target in a vacuum (application number is 202020286136.4), such as Figure 2 As shown. To this end, the rotary target needs to be installed in a vacuum. The problems with this type of rotary target built into a vacuum system are:

[0006] 1. The heat dissipation performance is poor. The rotating target can only dissipate heat through radiation scattering or through bearings, but cannot directly cool the high-temperature target surface through the cooling medium.

[0007] 2. The built-in rotating target can only use metal-lubricated bearings. This is because: first, using lubricating oil or grease would destroy the vacuum environment; second, the organic lubricant would evaporate or carbonize severely when the bearing operates at high temperatures. However, the lifespan of metal-lubricated bearings is very limited, generally only 50-100 hours, which is far from sufficient for the long-term operation requirements of accelerators.

[0008] For accelerators with higher electron energies (>0.6MeV), the aforementioned difficulties can be overcome by placing the rotating target externally. Specifically, a window is used to separate the electron beam line from the target cavity, allowing electrons to penetrate the window before striking the rotating target. Because the external rotating target does not operate in a vacuum, a circulating liquid can be used as a cooling medium for the X-ray conversion target (application number 201922198032.8). This type of rotating target also eliminates the need for metal-lubricated vacuum bearings. This external rotating target significantly improves heat dissipation efficiency, thereby significantly increasing the average power consumption of the accelerator.

[0009] However, the problem with this method of using an external rotating target with overall liquid cooling is that the electron beam inevitably has to penetrate a certain thickness of liquid, which causes electron scattering and an increase in the equivalent beam spot, making it difficult to achieve high-resolution imaging. In addition, the cooling liquid will also cause loss of electron energy and flux. On the other hand, the X-rays generated by electron target shooting also have to penetrate the cooling liquid, resulting in additional dose absorption. If the cooling liquid is used to cool only a portion of the rotating target, that is, it does not block the path of the electron beam and X-rays, the above problems can be alleviated. However, when part of the rotating target rotates at high speed in the liquid, it is easy to cause liquid splashing, thereby interfering with the transmission of the electron beam and X-rays. In addition, if the electron beam transmission window is damaged when using liquid to cool the external rotating target, the liquid will enter the vacuum pipe, causing contamination of the accelerator or even scrapping. Summary of the Invention

[0010] The technical problem to be solved by the present invention is that when the existing external rotating target with integral liquid cooling uses liquid to cool the target surface, the presence of liquid causes performance problems such as poor focus quality and dose loss. The purpose of the present invention is to provide an external rotating target assembly, X-ray source and method based on phase change cooling. The present invention uses a liquid droplet spray sprayed onto the target surface to achieve efficient heat dissipation through evaporation phase change, and then pumps away the high-temperature steam, thereby taking away the heat deposited by the electron beam in the rotating target. Since the steam will not significantly interfere with the electron beam or X-rays, it can ensure that the electron beam hits the target with better quality and the X-rays are emitted with minimal loss. Since the target cavity is evacuated by a vacuum pump, the cavity is in a low vacuum state. When liquid nitrogen spray cooling is used, it can be avoided that when the electron beam transmission window is damaged, the cooling liquid enters the beam pipe, thereby causing the accelerator to be scrapped.

[0011] The present invention is achieved through the following technical solutions:

[0012] In a first aspect, the present invention provides an external rotating target assembly based on phase change cooling, the rotating target assembly comprising a target cavity, a rotating target, a bearing, a driving coil, an atomizer, and an exhaust pipe;

[0013] A bearing and a drive coil are provided on one side of the target cavity, and an atomizer is provided on the other side; an exhaust pipe is connected to the bottom of the target cavity; a rotating target is installed in the target cavity through a bearing, and the rotating target is driven by the drive coil to achieve high-speed rotation;

[0014] When an external electron beam bombards a rotating target, it generates X-rays, with most of the energy deposited on the target as heat. An atomizer continuously sprays liquid mist onto the rotating target. When the hot area rotates to the corresponding position of the atomizer, the liquid mist droplets hit the hot rotating target and rapidly evaporate into hot gas. The hot gas is then extracted through an exhaust pipe, cooling the rotating target. The sprayed liquid mist can include liquid nitrogen, water, or organic liquids with high flash and ignition points.

[0015] The present invention utilizes phase-change cooling to cool the external rotating target. Because the evaporation phase change removes a large amount of heat, the high-temperature rotating target is rapidly cooled. Phase-change cooling of the mist droplets effectively exchanges heat. Furthermore, due to the low gas density and its rapid removal by the vacuum pump, the quality and dose of the electron beam and X-rays are not affected.

[0016] Furthermore, it also includes an air pump, which is connected to the exhaust pipe and is used to extract and cool the high-temperature gas through the exhaust pipe.

[0017] Furthermore, a condenser is connected to the bottom of the target cavity, which is used to discharge the condensate condensed from the high-temperature gas through the exhaust pipe; if the spray mist is sprayed with water or organic solvent, part of the gas will condense into liquid and be discharged through the set condenser.

[0018] Furthermore, there are multiple atomizers, one of which is arranged in the central area of the target cavity, and the remaining atomizers are symmetrically arranged on the circumference of the target cavity or evenly arranged on the circumference of the target cavity.

[0019] Furthermore, an electron transmission window is provided on one side of the upper end of the target cavity and a ray transmission window is provided on the other side. The electron beam passes through the electron transmission window from outside the electron transmission window and bombards the high-speed rotating target to generate X-rays; the X-rays penetrate the ray transmission window and are used for imaging and other applications.

[0020] Furthermore, the electron transmission window uses a thin film of a material with good thermal conductivity and low equivalent atomic number, such as beryllium, diamond, and aluminum; the thickness of the electron transmission window is between 10 microns and 0.3 mm.

[0021] The material of the rotary target is a high atomic number material or alloy such as tantalum, rhenium, tungsten, molybdenum or gold.

[0022] Furthermore, the rotary target assembly is adapted to electron energy of not less than 300 kV.

[0023] Furthermore, a shielding body is provided on the periphery of the bearing, and the shielding body is used to reduce the radiation dose inside the bearing.

[0024] Furthermore, the shielding body is made of heavy metal structural materials such as lead, lead alloy, and tungsten.

[0025] Furthermore, it also includes a heat exchanger and a water-cooled radiator, and the exhaust pipe is connected to the air pump through the heat exchanger;

[0026] A water-cooled radiator is also installed outside the target cavity, the water-cooled radiator is connected to the cooling system, and the cooling system is connected to the heat exchanger; the heat dissipation system cools the water-cooled radiator through circulating cooling water.

[0027] In a second aspect, the present invention further provides an X-ray source, the X-ray source further comprising a rotating target assembly, an accelerator, and a vacuum pipe, wherein the rotating target assembly adopts the external rotating target assembly based on phase change cooling;

[0028] accelerators, used to generate electron beams of a certain energy;

[0029] a vacuum duct for transmitting the electron beam to the rotating target assembly and passing through the electron transmission window;

[0030] a rotating target assembly, used for converting the electron beam transmitted from the vacuum pipe into X-rays, and emitting the X-rays from the radiation transmission window to the working area;

[0031] One side of the vacuum pipe is in a high vacuum state, and the target cavity of the rotating target assembly is in an atmospheric pressure or in a low vacuum state when the vacuum pump is working.

[0032] Furthermore, the vacuum conduit and the bearing are arranged on the same side of the target cavity, or on different sides of the target cavity. In the above technical solution, when the vacuum conduit and the bearing are arranged on the same side of the target cavity, the X-ray irradiation field is larger; when the vacuum conduit and the bearing are arranged on different sides of the target cavity, it is convenient to install a larger electron beam focusing structure to obtain a smaller electron beam focal spot.

[0033] In a third aspect, the present invention further provides a phase change cooling method for an external accelerator rotating target, which is applied to the external rotating target assembly based on phase change cooling; the method comprises:

[0034] The electron beam generated by an accelerator or a high-voltage device passes through the electron transmission window of the rotating target assembly and bombards the rotating target outside the vacuum to generate X-rays;

[0035] By spraying droplets onto the rotating target surface, the target surface is efficiently dissipated through liquid evaporation, and the high-temperature vapor formed by phase change is extracted, thereby ultimately taking away the heat deposited by the electron beam in the rotating target and cooling it.

[0036] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0037] The present invention relates to an external rotating target assembly, an X-ray source, and a method based on phase change cooling. Under the same power density conditions, compared with the external rotating target method using liquid overall cooling, the cooling of the external rotating target of the present invention is achieved by a phase change cooling method. Since the evaporation phase change takes away a large amount of heat, the high-temperature rotating target (2) is quickly cooled; and the phase change cooling of the droplets can effectively exchange heat. At the same time, since the gas density is low and it is quickly pumped away by the vacuum pump, the vapor will not significantly interfere with the electron beam or X-rays. The electron beam is focused without being scattered by the liquid, so that the target is hit with a smaller beam spot size to obtain better X-ray spatial resolution; the electron flux and X-ray dose will not be lost due to absorption by the cooling liquid. By using multiple sprayers arranged in a reasonable manner, the target surface tilt or jump caused by the spray pressure can be avoided.

[0038] In addition, the target cavity is evacuated by a vacuum pump, and the cavity is in a low vacuum state. When using liquid nitrogen spray cooling, it can prevent the cooling liquid from entering the beam pipe when the electron beam transmission window is damaged, which may cause the accelerator to be scrapped. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] 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:

[0040] Figure 1 This is a schematic diagram of the structure of a fixed solid transmission target in the prior art.

[0041] Figure 2 This is a schematic diagram of the structure of a transmission-type solid rotating target in the prior art.

[0042] Figure 3 This is a schematic diagram of an external rotating target assembly, X-ray source, and method based on phase change cooling according to the present invention.

[0043] Figure 4 This is a schematic diagram of the structure of an external rotating target assembly and an X-ray source based on phase change cooling in the present invention. Figure 1 .

[0044] Figure 5 This is a schematic diagram of the structure of an external rotating target assembly and an X-ray source based on phase change cooling in the present invention. Figure 2 .

[0045] Figure 6 Schematic diagram of the multi-atomizer of the present invention.

[0046] Figure 7 Schematic diagram of the torque balance of the multi-atomizer of the present invention.

[0047] Figure 8 Schematic diagram of the arrangement of the radiator and heat exchanger of the present invention.

[0048] Figure 9 A schematic diagram of the cooling medium circulated in the present invention, wherein the vapor is re-condensed or compressed through an exchanger or compressor to re-form a condensed liquid, which is circulated through a conduit to be provided to the sprayer for use.

[0049] Figure 10 This is a schematic diagram of the present invention using a drive motor to directly drive a vacuum dynamic seal bearing fixed on the target cavity.

[0050] Reference numerals and corresponding component names:

[0051] 1-target chamber, 2-rotating target, 3-bearing, 4-driving coil, 5-atomizer, 6-exhaust pipe, 7-vacuum pump, 8-condenser, 9-shielding body, 10-electron transmission window, 11-ray transmission window, 12-accelerator, 13-vacuum pipe, 14-heat exchanger, 15-water-cooled radiator. DETAILED DESCRIPTION

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] The existing external rotating target based on liquid overall cooling uses liquid to cool the target surface, but the presence of liquid causes performance problems such as poor focus quality and dose loss. Therefore, the present invention designs an external rotating target assembly, X-ray source and method based on phase change cooling. The working principle of the present invention is as follows: Figure 3 As shown, a thin window (i.e., electron transmission window 10) made of low atomic number, high thermal conductivity material separates the vacuum pipe 13 from the target cavity. An external rotating target is used to convert the electron beam into X-rays. It is mounted in the target cavity via bearings and rotates at high speed driven by an external drive motor. The external rotating target is cooled using a phase change cooling method. The vacuum pipe 13 is connected to the accelerator 12 for electron transmission. After the electron beam passes through the electron transmission window 10, it strikes the high-speed rotating target, generating X-rays. The X-rays then pass through the ray transmission window for imaging and other applications.

[0059] Most of the power of the electron beam is deposited in the target, so that the temperature of the target can reach hundreds of degrees Celsius. Therefore, one or more atomizers 5 are arranged on the target cavity to spray liquid spray onto the target surface. The liquid spray evaporates rapidly and takes away a large amount of heat, thereby taking away the heat deposited by the electron beam in the rotating target, so that the temperature of the target is controlled within a reasonable range, and the target is prevented from burning due to overheating. Since the steam will not significantly interfere with the electron beam or X-rays, it can be ensured that the electron beam hits the target with better quality, and the X-rays are also emitted with minimal loss. Since the target cavity is evacuated by a vacuum pump, the cavity is in a low vacuum state. When liquid nitrogen spray cooling is used, it can be avoided that when the electron beam transmission window is damaged, the cooling liquid enters the beam pipe, causing the accelerator to be scrapped.

[0060] The present invention proposes for the first time an external rotating target, X-ray source and method based on phase change cooling. Based on this technology, the power of the rotating target can be greatly improved while ensuring the quality of the electron beam and X-rays. It is suitable for various application scenarios such as high-average-power precision X-ray imaging.

[0061] Example 1

[0062] like Figures 3 to 5 As shown, the present invention is an external rotating target assembly based on phase change cooling, which includes a target cavity 1, a rotating target 2, a bearing 3, a driving coil 4, an atomizer 5 and an exhaust pipe 6;

[0063] A bearing 3 and a drive coil 4 are provided on one side of the target cavity 1, and an atomizer 5 is provided on the other side. An exhaust pipe 6 is connected to the bottom end of the target cavity 1. The rotating target 2 is installed in the target cavity 1 through the bearing 3. The rotating target 2 rotates at high speed under the drive of the drive coil 4.

[0064] When the external electron beam bombards the rotating target 2, it generates X-rays. Most of the energy is deposited on the rotating target 2 as heat. The atomizer 5 continuously sprays liquid mist toward the rotating target 2. When the high-temperature position rotates to the corresponding position of the atomizer 5, the liquid mist droplets hit the high-temperature rotating target 2 and rapidly evaporate into high-temperature gas. The high-temperature gas is then extracted through the exhaust pipe 6, thereby cooling the rotating target 2. The sprayed liquid mist may include liquid nitrogen, water, or organic liquids with high flash points and ignition points.

[0065] The present invention utilizes phase-change cooling to cool the external rotating target. Because the evaporation phase change removes a significant amount of heat, the high-temperature rotating target 2 is rapidly cooled. Phase-change cooling of the mist droplets effectively exchanges heat. Furthermore, due to the low gas density and its rapid removal by the vacuum pump 7, the quality and dose of the electron beam and X-rays are not affected.

[0066] As a further implementation, the electron beam focal spot diameter is less than 2 mm, and the electron beam continuous power is greater than 100W.

[0067] As a further implementation, the rotation speed of the rotary target 2 is 1000-35000 rpm.

[0068] As a further implementation, an air pump 7 is further included, which is connected to the exhaust pipe 6 and is used to extract and cool the high-temperature gas through the exhaust pipe 6.

[0069] As a further implementation, a condenser 8 is also connected to the bottom of the target cavity 1, which is used to discharge the condensate condensed from the high-temperature gas through the exhaust pipe 6; if the spray liquid mist is sprayed with water or organic solvent, part of the gas will condense into liquid and be discharged through the set condenser 8.

[0070] As a further implementation, in order to further improve the cooling efficiency or reduce the damage to the target caused by the temperature shock caused by a single phase change cooling, multiple atomizers 5 can be used simultaneously to cool the high temperature area of the rotating target 2; in order to reduce the heat transferred from the target to the bearing 3, one of the atomizers 5 is arranged in the central area of the target cavity 1, and phase change cooling is performed on the central area, such as Figure 6 shown.

[0071] In addition, since the rotating target 2 rotates at high speed during operation, the high-speed droplet spraying on the rotating target 2 generates pressure. The pressure is concentrated on one side, which causes the rotating target 2 to be unbalanced and causes the target surface of the rotating target 2 to tilt and jump, which is not conducive to ensuring the X-ray focal spot and the long life of the bearing 3. Therefore, further, the remaining multiple sprayers are arranged symmetrically on the circumference of the target cavity 1 (that is, arranged two by two on a diameter) or evenly on the circumference of the target cavity 1, so that the resultant force of the above pressure is at the center of the rotating target 2, such as Figure 7 shown.

[0072] As a further implementation, an electron transmission window 10 is required to isolate the target cavity 1 from the vacuum conduit 13 used for electron beam transmission from the accelerator 12. One side of the vacuum conduit 13 is in a high vacuum state, while the target cavity 1 is at atmospheric pressure or, when the vacuum pump 7 is operating, in a low vacuum state. X-rays generated by the electron beam bombarding the target also pass through the electron transmission window 10 before being used for imaging and other applications. Transmission windows are categorized as electron transmission windows 10 and radiation transmission windows, depending on the material they transmit.

[0073] An electron transmission window 10 is provided on one side of the upper end of the target cavity 1, and a ray transmission window 11 is correspondingly provided on the other side. The electron beam passes through the electron transmission window 10 from outside the electron transmission window 10, bombards the high-speed rotating target 2, and generates X-rays; the X-rays penetrate the ray transmission window and are used for imaging and other applications.

[0074] Among them, the electron transmission window 10 needs to be isolated from vacuum and atmospheric pressure, so it requires good strength; in order to ensure that as many electrons as possible pass through with minimal energy loss, low atomic number materials need to be used; since the electron beam is focused, the diameter of the electron beam is generally less than 2 mm, so the diameter of the electron transmission window 10 is also relatively small; in summary, the electron transmission window 10 uses diamond, beryllium, aluminum and its alloys, and composite materials with a thickness of less than 0.3 mm and a diameter of less than 5 mm.

[0075] As a further implementation, the material of the rotary target 2 is a high atomic number material or alloy such as tantalum, rhenium, tungsten, molybdenum or gold.

[0076] As a further implementation, the rotating target assembly is suitable for electron energies of no less than 300 kV. The higher the electron energy, the greater the advantages of the vacuum liquid circulation target technology. Because the electron transmission window 10 has a certain thickness, if the electron beam energy is too low, most of the electron power will be deposited in the electron transmission window 10. The low atomic number of the electron transmission window 10 results in low X-ray conversion efficiency.

[0077] As a further implementation, considering that X-ray irradiation may cause the organic lubricating material used in the bearing 3 to degenerate, a shielding body 9 is provided on the periphery of the bearing 3 , and the shielding body 9 is used to reduce the radiation dose inside the bearing 3 .

[0078] The shielding body 9 can be made of heavy metal structural materials such as lead, lead alloy, tungsten, etc.

[0079] As a further implementation, a heat exchanger 14 and a water-cooled radiator 15 are further included, and the exhaust pipe 6 is connected to the air extraction pump 7 through the heat exchanger 14;

[0080] A water-cooled radiator 15 is also installed outside the target cavity 1. The water-cooled radiator 15 is connected to a cooling system, and the cooling system is connected to the heat exchanger 14. The cooling system cools the water-cooled radiator 15 by circulating cooling water.

[0081] The technical solutions of the present invention all require the use of an air pump 7 to remove the large amount of high-temperature gas generated during the phase change heat dissipation process. In order to avoid damaging the air pump 7, a heat exchanger is used to cool the high-temperature gas first. In addition, since the high-temperature gas generated by the phase change will cause the target cavity 1 to be heated, the target cavity 1 is cooled by a water-cooled radiator. The heat of the radiator and the heat exchanger is finally exchanged through the cooling system, such as Figure 8 shown.

[0082] For high-value, recyclable cooling media, such as liquid nitrogen, organic coolant, etc., the vapor can be re-condensed or compressed through a heat exchanger or compressor to form a condensed liquid, which is then circulated through a conduit to the sprayer. Figure 9 shown.

[0083] In addition to using the drive coil 4 to drive the bearing through magnetic field coupling, a drive motor can also be used to directly drive the vacuum dynamic seal bearing fixed on the target cavity 1; the bearing can include ordinary grease lubricated bearings or magnetic fluid bearings, which are not limited in this invention. Figure 10 shown.

[0084] Example 2

[0085] like Figure 4 and Figure 5 As shown, the difference between this embodiment and embodiment 1 is that this embodiment provides an X-ray source, which further includes a rotating target assembly, an accelerator 12 and a vacuum pipe 13. The rotating target assembly adopts the external rotating target assembly based on phase change cooling described in embodiment 1;

[0086] An accelerator 12 is used to generate an electron beam of a certain energy, specifically using electrostatic field acceleration or microwave field acceleration;

[0087] The vacuum pipe 13 is used to transmit the electron beam and focus the electron beam to a desired size through focusing elements such as a focusing coil; and to pass the electron beam through the electron transmission window 10 and then enter the target cavity 1 of the rotating target assembly;

[0088] The rotating target assembly is used to convert the electron beam transmitted from the vacuum pipe into X-rays (i.e., the electron beam generates X-rays by bombarding the rotating target 2, and the X-rays are emitted to the working area through the ray transmission window 11;

[0089] One side of the vacuum pipe 13 is in a high vacuum state, and the target cavity 1 of the rotating target assembly is at atmospheric pressure or is in a low vacuum state when the vacuum pump 7 is working;

[0090] As a further implementation, the vacuum pipe 13 and the bearing 3 are arranged on the same side of the target cavity 1 , or the vacuum pipe 13 and the bearing 3 are arranged on different sides of the target cavity 1 .

[0091] In the above technical solution, when the vacuum pipe 13 and the bearing 3 are arranged on the same side of the target cavity 1, the irradiation field of the X-ray is larger. Figure 4 When the vacuum pipe 13 and the bearing 3 are arranged on different sides of the target cavity 1, it is beneficial to install a larger electron beam focusing structure to obtain a smaller electron beam focal spot, such as Figure 5 shown.

[0092] Example 3

[0093] like Figures 1 to 10 As shown, the difference between this embodiment and embodiment 1 is that this embodiment provides a phase change cooling method for an external accelerator rotating target, which is applied to the external rotating target assembly based on phase change cooling described in embodiment 1; the method includes:

[0094] The electron beam generated by an accelerator or a high-voltage device passes through the electron transmission window of the rotating target assembly and bombards the rotating target outside the vacuum to generate X-rays;

[0095] By spraying droplets onto the rotating target surface, the target surface is efficiently dissipated through liquid evaporation, and the high-temperature vapor formed by phase change is extracted, thereby ultimately taking away the heat deposited by the electron beam in the rotating target and cooling it.

[0096] After the electron beam passes through an electron transmission window, it strikes a rotating target outside a vacuum. Phase-change cooling technology significantly increases the power density of the rotating target X-ray source. This invention addresses the problems associated with using liquid to cool an external rotating target: electron scattering by the liquid hinders the achievement of a microbeam spot, liquid absorption leads to significant dose loss, and transmission window rupture can contaminate or render the accelerator useless.

[0097] 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. An external rotating target assembly based on phase change cooling, characterized in that: The rotating target assembly comprises a target cavity (1), a rotating target (2), a bearing (3), a driving coil (4), an atomizer (5) and an exhaust pipe (6); A bearing (3) and a driving coil (4) are provided on one side of the target cavity (1), and an atomizer (5) is provided on the other side; an exhaust pipe (6) is connected to the bottom end of the target cavity (1); the rotating target (2) is installed in the target cavity (1) via the bearing (3), and the rotating target (2) is driven by the driving coil (4) to achieve high-speed rotation; When the external electron beam bombards the rotating target (2), X-rays are generated by bombarding the rotating target (2), and part of the energy is deposited on the rotating target (2) in the form of heat; the atomizer (5) continuously sprays liquid mist toward the rotating target (2), and when the high-temperature position rotates to the position corresponding to the atomizer (5), the liquid mist droplets hit the high-temperature rotating target (2) and evaporate into high-temperature gas, and the high-temperature gas is extracted through the exhaust pipe (6) to achieve cooling of the rotating target; the vapor will not interfere with the electron beam or X-rays; the electron beam is focused without being scattered by the liquid, and the rotating target (2) is hit with a smaller beam spot size to obtain better X-ray spatial resolution; the electron flux and X-ray dose will not be lost due to absorption by the cooling liquid.

2. The external rotating target assembly based on phase change cooling according to claim 1, characterized in that: It also includes an air extraction pump (7), which is connected to the exhaust pipe (6) and is used to extract and cool the high-temperature gas through the exhaust pipe (6).

3. The external rotating target assembly based on phase change cooling according to claim 1 or 2, characterized in that: The bottom end of the target cavity (1) is also connected to a condenser tube (8), and the condenser tube (8) is used to discharge condensate formed by condensing the high-temperature gas through the exhaust pipe (6).

4. The external rotating target assembly based on phase change cooling according to claim 1, characterized in that: There are multiple atomizers (5), one of which is arranged in the central area of the target cavity (1), and the remaining atomizers (5) are symmetrically arranged on the circumference of the target cavity (1) or evenly arranged on the circumference of the target cavity (1).

5. The external rotating target assembly based on phase change cooling according to claim 1, characterized in that: An electron transmission window (10) is provided on one side of the upper end of the target cavity (1), and a ray transmission window (11) is correspondingly provided on the other side. The electron beam passes through the electron transmission window (10) from outside the electron transmission window (10) and bombards the high-speed rotating target (2), thereby generating X-rays.

6. The external rotating target assembly based on phase change cooling according to claim 1, characterized in that: A shielding body (9) is provided on the periphery of the bearing (3), and the shielding body (9) is used to reduce the radiation dose inside the bearing (3).

7. The external rotating target assembly based on phase change cooling according to claim 2, characterized in that: It also includes a heat exchanger (14) and a water-cooled radiator (15), and the exhaust pipe (6) is connected to the air pump (7) through the heat exchanger (14); A water-cooled radiator (15) is also installed outside the target cavity (1), and the water-cooled radiator (15) is connected to a cooling system, and the cooling system is connected to a heat exchanger (14); the cooling system cools the water-cooled radiator (15) by circulating cooling water.

8. An X-ray source, characterized in that: The X-ray source further comprises a rotating target assembly, an accelerator (12) and a vacuum pipe (13), wherein the rotating target assembly adopts an external rotating target assembly based on phase change cooling as claimed in any one of claims 1 to 7; The accelerator (12) is used to generate an electron beam with a preset energy; The vacuum pipe (13) is used to transmit the electron beam to the rotating target assembly and pass through the electron transmission window (10); The rotating target assembly is used to convert the electron beam transmitted from the vacuum pipe into X-rays, and emit the X-rays from the ray transmission window (11) to the working area; One side of the vacuum pipe (13) is in a high vacuum state, and the target cavity (1) of the rotating target assembly is in an atmospheric pressure or in a low vacuum state when the vacuum pump is working.

9. An X-ray source according to claim 8, characterized in that: The vacuum pipe (13) and the bearing (3) are arranged on the same side of the target cavity (1), or the vacuum pipe (13) and the bearing (3) are arranged on different sides of the target cavity (1).

10. A phase change cooling method for an external accelerator rotating target, characterized in that: The method is applied to an external rotating target assembly based on phase change cooling as described in any one of claims 1 to 7; the method comprises: The electron beam generated by the accelerator passes through the electron transmission window of the rotating target assembly and bombards the rotating target outside the vacuum to generate X-rays; By spraying liquid droplets onto the rotating target surface, the heat of the rotating target is dissipated by liquid evaporation, and the high-temperature vapor formed by phase change is extracted, thereby ultimately taking away the heat deposited by the electron beam in the rotating target and cooling it.

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