Linear accelerator

Abstract

The invention relates to the technical field of linear accelerators, in particular to a linear accelerator which comprises an accelerating tube, an input coupler inclined waveguide, an output coupler inclined waveguide, a first drift tube, a second drift tube and a water temperature adjusting structure. The accelerating tube is composed of a plurality of accelerating cavities and a plurality of fence pieces. The input coupler inclined waveguide is communicated with the input coupling cavity; the output coupler inclined waveguide is communicated with the output coupling cavity; the first drift tube is communicated with the input coupling cavity; the second drift tube is communicated with the output coupling cavity; the water temperature adjusting structure comprises a spiral water pipe, a first water distribution ring, a second water distribution ring and a water pipe outer sleeve. Heat generated by the accelerating tube is taken away through circulating water flow, the working temperature of the accelerating tube is effectively controlled, it is guaranteed that the temperature of the accelerating tube is evenly distributed, and the service life of the accelerator is prolonged; meanwhile, the beam current transmission efficiency is 83.18%, the conversion efficiency from RF to the beam current is 78.21%, and the beam current power can reach 28 kW to 35 kW.

Description

Technical Field

[0001] The present invention relates to the technical field of linear accelerators, and in particular to a linear accelerator. Background Art

[0002] With the increasing popularity of nuclear technology, irradiation technology has become an important processing method with its unique advantages. Compared with traditional chemical treatment and heat treatment methods, irradiation technology has the characteristics of high efficiency, environmental protection, and strong controllability. Especially in the modification of materials, sterilization and disinfection, and food preservation, irradiation technology can significantly improve the treatment effect, extend the service life of the product, and reduce pollution to the environment. Electron accelerators are widely used as one of the stable and reliable irradiation sources.

[0003] An electron accelerator is a device that uses an electric field to accelerate and utilize electrons. It is widely used in many fields, including material modification, disinfection and sterilization, food preservation, semiconductor manufacturing, and waste treatment. By accelerating electrons and directing them to the material to be processed, electron accelerators can achieve efficient and pollution-free irradiation processing. Existing commonly used electron accelerators can be divided into three categories according to their energy range: (1) Low-energy accelerators (80keV-300keV), mainly represented by electron curtain accelerators. It is a high-voltage accelerator but does not have an acceleration sleeve and scanning device. It has the characteristics of simple structure, small size, and self-shielding. The beam power is generally 150kW to 200kW. This type of accelerator is mainly used for radiation treatment of thin-layer materials or surface coatings; (2) Medium-energy accelerators (0.3MeV-5MeV), mainly represented by ground-nano accelerators, whose power can reach tens or even hundreds of kilowatts, are mainly used in the fields of radiation cross-linking of polyethylene insulation materials and polyethylene foam plastic materials for wires and cables; (3) High-energy accelerators (5MeV-10MeV), mainly electron linear accelerators, which use microwaves to accelerate particles. According to the type of microwave used, they can be divided into traveling wave accelerators and standing wave accelerators. The electron energy output of this type of accelerator is relatively high, with an output power of several kilowatts or even tens of kilowatts, but due to industrial radiation safety restrictions, the maximum energy is generally 10MeV. This type of accelerator is mainly used for irradiation sterilization of medical drugs and foods, modification of electronic components, and tire vulcanization. Compared with the other two types of accelerators, electron linear accelerators have the characteristics of high energy, precise control, and diverse functions, and are used in a wider range of scenarios.

[0004] In the related art, the application number is 201920891271.9, a low-energy, high-current, strong traveling wave accelerating tube, including an accelerating tube body, the two ends of the accelerating tube body are respectively connected with an input coupler and an output coupler; the accelerating tube body is a disk-loaded waveguide, and seven accelerating chambers are arranged inside, and adjacent accelerating chambers are separated by a disk, and the length of the accelerating chamber after segmentation is increased by 1.2 times; wherein the first to sixth accelerating chambers are bunching chambers, and the seventh accelerating chamber is a light speed chamber. By arranging a number of uniformly changing accelerating chambers in the accelerating tube, as well as input and output couplers at both ends of the accelerating tube, the output electron beam energy can reach the megavolt level and the power is greater than 1kW, while having the advantages of small size, compact structure and easy protection. However, the above structure still has the following problems: during the long-term operation of the accelerating tube, the accelerating tube is prone to temperature rise due to heat accumulation, which in turn affects the performance and stability of the accelerator. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the purpose of the present invention is to provide a linear accelerator, whose water temperature regulating structure takes away the heat generated by the accelerating tube through the circulating water flow, effectively controls the working temperature of the accelerating tube, ensures the temperature of the accelerating tube is evenly distributed, and prolongs the service life of the accelerator.

[0006] The first aspect of the present invention provides a linear accelerator, comprising an accelerating tube, an input coupler oblique waveguide, an output coupler oblique waveguide, a first drift tube, a second drift tube and a water temperature regulating structure;

[0007] The accelerating tube is composed of a plurality of accelerating cavities and a plurality of fences; each accelerating cavity is welded with a fence to form a complete accelerating structure, and all accelerating structures are welded to form an accelerating tube body, wherein a beam hole is arranged on each fence, so that all accelerating cavities are interconnected to form a complete beam transmission path; wherein the first cavity along the moving direction of the electron beam is an input coupling cavity, and the last cavity along the moving direction of the electron beam is an output coupling cavity;

[0008] The input coupler oblique waveguide is in communication with the input coupling cavity and is used to introduce external radio frequency power into the accelerator;

[0009] The output coupler oblique waveguide is in communication with the output coupling cavity and is used to output the remaining microwave power;

[0010] The first drift tube is in communication with the input coupling cavity, and is used to provide a passage for the electron beam to enter the acceleration cavity;

[0011] The second drift tube is in communication with the output coupling cavity, and is used to provide a channel for the accelerated electron beam to leave the accelerating cavity;

[0012] The water temperature regulating structure includes a spiral water pipe, a first water diversion ring, a second water diversion ring and a water pipe jacket; the first water diversion ring is arranged on the first drift tube, and the second water diversion ring is arranged on the second drift tube; the spiral water pipe is coiled on the outer wall of the accelerating tube body, one end of which is connected to the first water diversion ring, and the other end of which is connected to the second water diversion ring; the water pipe jacket is sleeved on the outside of the spiral water pipe.

[0013] In the first aspect of the present invention, as a preferred embodiment, the water pipe sleeve includes a first sleeve and a second sleeve, the first sleeve is sleeved on the outside of the spiral water pipe, the second sleeve is sleeved on the outside of the second sleeve, and a gap is formed between the second sleeve and the first sleeve.

[0014] In the first aspect of the present invention, as a preferred embodiment, one end of the accelerating tube body is sealed and connected to the first drift tube via a first flange, and the other end thereof is sealed and connected to the second drift tube via a second flange.

[0015] In the first aspect of the present invention, as a preferred embodiment, a first pipe joint is provided on the first drifter, the water outlet end of the first pipe joint is communicated with the first water dividing ring, and the water inlet end thereof is used to communicate with the water outlet of the cooling system;

[0016] The second drifter is provided with a second pipe joint, the water inlet end of the second pipe joint is connected with the second water dividing ring, and the water outlet end thereof is used to be connected with the water inlet of the cooling system.

[0017] In the first aspect of the present invention, as a preferred embodiment, the acceleration chamber includes a phase-changing speed section and a light speed section which are sequentially connected along the moving direction of the electron beam; the phase-changing speed section is used to focus and phase-slide the electron beam, and the light speed section is used to increase the energy of the electron beam.

[0018] In the first aspect of the present invention, as a preferred embodiment, the number of accelerating cavities is sixty, wherein the cavity of the first accelerating cavity to the third accelerating cavity along the electron beam movement direction is mainly used for bunching, the cavity of the fourth to the seventh accelerating cavity is mainly used for phase sliding, and the cavity of the eighth to the sixtieth accelerating cavity constitutes a light speed segment; the cavity of the first accelerating cavity is an input coupling cavity, and the cavity of the sixtieth accelerating cavity is an output coupling cavity.

[0019] In the first aspect of the present invention, as a preferred embodiment, the edge of the beam hole forms an elliptical structure; the total length of the accelerating chamber is 2043.054 mm, the thickness of the fence is 5.5 mm; the ratio of the major and minor axes of the elliptical structure of the beam hole edge is 1.8:1.

[0020] In the first aspect of the present invention, as a preferred embodiment, the input coupling cavity is a cylindrical inner cavity structure, the output coupling cavity is a cylindrical inner cavity structure, and the cavity bodies of the remaining acceleration cavities are composed of two symmetrical bowl-shaped inner cavity structures.

[0021] In the first aspect of the present invention, as a preferred embodiment, the apertures of the beam holes of all fences decrease successively; the cavity radius of the accelerating cavity of the phase-changing speed section increases successively along the moving direction of the electron beam, the cavity radius of the first accelerating cavity reaching the light speed section reaches a maximum value, and the cavity radius of the accelerating cavity of the light speed section decreases successively along the moving direction of the electron beam; the cavity length of the accelerating cavity of the phase-changing speed section gradually increases along the moving direction of the electron beam, and the cavity length of the accelerating cavity of the light speed section remains unchanged.

[0022] In the first aspect of the present invention, as a preferred embodiment, the phase velocity βp of the RF field in the phase-changing speed section gradually transitions from 0.54 to 1, and the phase velocity βp of the RF field in the light speed section is 1.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The acceleration process of this embodiment: the external RF power enters the input coupling cavity through the input coupler oblique waveguide to form a high-frequency electric field. The electron beam enters the input coupling cavity from the first drift tube and is accelerated by the high-frequency electric field. The electron beam passes through each chamber in turn, is accelerated once in each chamber until it leaves the accelerating tube, and is also accelerated in the output coupling cavity. In the output coupling cavity, the electron beam is finally accelerated, and the finally accelerated electron beam smoothly leaves the accelerating tube through the output coupler oblique waveguide. Temperature adjustment process: the cooling water enters the spiral water pipe from the first water distribution ring and flows along the outer wall of the accelerating tube body. During the flow process, the cooling water exchanges heat with the accelerating tube body and takes away the heat generated by the accelerating tube body. The heated cooling water flows out of the spiral water pipe through the second water distribution ring, enters the cooling system for cooling and then is recycled. The water pipe jacket protects the water pipe from external damage and enhances the heat exchange effect. By adjusting the flow and temperature of the circulating water flow, the operating temperature of the accelerating tube body can be accurately controlled, and the temperature difference of the entire accelerating tube body is less than 0.5 degrees Celsius. When the temperature of the accelerating tube body increases, the flow rate of the water flow can be increased or the water temperature can be reduced; conversely, when the temperature of the accelerating tube body decreases, the flow rate of the water flow can be reduced or the water temperature can be increased. In this way, the water temperature regulating structure of the present invention takes away the heat generated by the accelerating tube body through the circulating water flow, effectively controls the working temperature of the accelerating tube body, ensures that the temperature of the accelerating tube body is evenly distributed, and prolongs the service life of the accelerator.

[0025] 2. Compared with the commonly used accelerating tubes with equal impedance, the ratio of the peak accelerating electric field gradient to the average accelerating electric field gradient in the accelerating tube designed in the present invention is lower, but it has a more uniform RF (Radio Frequency) power consumption distribution; under the same attenuation coefficient τ, the RF conversion efficiency is higher; the threshold current of the beam collapse effect that affects the beam power increase is higher. Through simulation, the performance of the accelerating tube designed in the present invention is as follows: the beam transmission efficiency is 83.18%, the RF to beam conversion efficiency is 78.21%, and the beam power can reach 28kW to 35kW, which is much higher than the current conventional accelerating tubes with equal impedance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of the linear accelerator of the present invention;

[0027] Figure 2 It is a structural schematic diagram of the linear accelerator of the present invention from another angle;

[0028] Figure 3 is a cross-sectional view of a linear accelerator of the present invention;

[0029] Figure 4 It is a structural schematic diagram of a linear accelerator of the present invention without input coupler oblique waveguide and output coupler oblique waveguide;

[0030] Figure 5 It is a schematic diagram of the separate structure of the spiral water pipe and the water pipe jacket of the present invention;

[0031] Figure 6 It is a partial structural cross-sectional view of the accelerating tube of the present invention;

[0032] Figure 7 It is a schematic diagram of the structure of the accelerating tube of the present invention;

[0033] Figure 8 It is a schematic structural diagram of the accelerating tube of the present invention from another angle.

[0034] In the figure:

[0035] 100, accelerating tube; 10, accelerating tube body; 11, accelerating cavity; 110, accelerating cavity body; 111, phase-changing speed section; 112, light speed section; 113, input coupling cavity; 114, output coupling cavity; 20, fence; 21, beam hole;

[0036] 200, input coupler slanted waveguide;

[0037] 300, output coupler slanted waveguide;

[0038] 400, a first drift tube; 410, a first pipe joint;

[0039] 500, second drift tube; 510, second pipe joint;

[0040] 600, water temperature regulating structure; 610, spiral water pipe; 620, first water distribution ring; 630, second water distribution ring; 640, water pipe jacket; 641, first sleeve; 642, second sleeve;

[0041] 700, first flange;

[0042] 800. Second flange. DETAILED DESCRIPTION

[0043] Below, in conjunction with the accompanying drawings and specific embodiments, the invention is further described. It should be noted that, under the premise of no conflict, the various embodiments described below or the various technical features can be arbitrarily combined to form a new embodiment. Except as otherwise specified, the materials and equipment used in this embodiment can be purchased from the market. Examples of the embodiments are shown in the accompanying drawings, in which the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0044] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present application. In the description of the present application, "plurality" means two or more, unless otherwise precisely and specifically specified.

[0045] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "connected", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, or it can be connected through an intermediary medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0046] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0047] Please refer to Figure 1-8 As shown, this embodiment provides a linear accelerator, including an accelerating tube 100, an input coupler oblique waveguide 200, an output coupler oblique waveguide 300, a first drift tube 400, a second drift tube 500 and a water temperature regulating structure 600;

[0048] The accelerating tube 100 is composed of a plurality of accelerating cavities 11 and a plurality of fences 20; each accelerating cavity 11 is welded with a fence 20 to form a complete accelerating structure, and all accelerating structures are welded to form an accelerating tube body 10, wherein a beam hole 21 is provided on each fence 20, so that all accelerating cavities 11 are interconnected to form a complete beam transmission path; wherein the cavity 110 of the first accelerating cavity along the electron beam moving direction is an input coupling cavity 113, and the cavity 110 of the last accelerating cavity along the electron beam moving direction is an output coupling cavity 114;

[0049] The input coupler oblique waveguide 200 is in communication with the input coupling cavity 113 and is used to introduce external radio frequency power into the accelerator;

[0050] The output coupler oblique waveguide 300 is in communication with the output coupling cavity 114 and is used to output the remaining microwave power;

[0051] The first drift tube 400 is in communication with the input coupling cavity 113 and is used to provide a channel for the electron beam to enter the acceleration cavity 11;

[0052] The second drift tube 500 is in communication with the output coupling cavity 114 and is used to provide a channel for the accelerated electron beam to leave the accelerating cavity 11;

[0053] The water temperature regulating structure 600 includes a spiral water pipe 610, a first water diversion ring 620, a second water diversion ring 630 and a water pipe jacket 640; the first water diversion ring 620 is arranged on the first drift tube 400, and the second water diversion ring 630 is arranged on the second drift tube 500; the spiral water pipe 610 is coiled on the outer wall of the accelerating tube body 10, one end of which is connected to the first water diversion ring 620, and the other end of which is connected to the second water diversion ring 630; the water pipe jacket 640 is sleeved on the outside of the spiral water pipe 610.

[0054] On the basis of the above structure, the acceleration process: the external RF power enters the input coupling cavity 113 through the input coupler oblique waveguide 200 to form a high-frequency electric field. The electron beam enters the input coupling cavity 113 from the first drift tube 400 and is accelerated by the high-frequency electric field. The electron beam passes through the cavity 110 of each accelerating cavity in turn, and is accelerated once in the cavity 110 of each accelerating cavity until it reaches the output coupling cavity 114. In the output coupling cavity 114, the electron beam is finally accelerated, and the finally accelerated electron beam leaves the accelerating tube smoothly through the second drift tube 500. Temperature adjustment process: cooling water enters the spiral water pipe 610 from the first water dividing ring 620 and flows along the outer wall of the accelerating tube body 10. During the flow process, the cooling water exchanges heat with the accelerating tube body 10 and takes away the heat generated by the accelerating tube body 10. The heated cooling water flows out of the spiral water pipe 610 through the second water dividing ring 630, enters the cooling system for cooling and then is recycled. The water pipe jacket 640 protects the water pipe from external damage and enhances the heat exchange effect. By adjusting the flow rate and temperature of the circulating water flow, the operating temperature of the accelerating tube body 10 can be accurately controlled, and the temperature difference of the entire accelerating tube body 10 is less than 0.5 degrees Celsius. When the temperature of the accelerating tube body 10 increases, the flow rate of the water flow can be increased or the water temperature can be reduced; conversely, when the temperature of the accelerating tube body 10 decreases, the flow rate of the water flow can be reduced or the water temperature can be increased.

[0055] In this way, the water temperature regulating structure 600 of the present invention takes away the heat generated by the accelerating tube body 10 through the circulating water flow, effectively controls the working temperature of the accelerating tube body 10, ensures the uniform temperature distribution in the accelerating tube body 10, and prolongs the service life of the accelerator.

[0056] As a preferred embodiment, the water pipe sleeve 640 includes a first sleeve 641 and a second sleeve 642. The first sleeve 641 is sleeved on the outside of the spiral water pipe 610, and the second sleeve 642 is sleeved on the outside of the second sleeve 642. A gap is formed between the second sleeve 642 and the first sleeve 641.

[0057] During the operation of the accelerator, cooling water flows through the spiral water pipe 610 to take away the heat generated by the accelerating tube body 10. The double-layer sleeve structure serves as the water pipe outer jacket 640, and through its heat insulation and protection functions, it ensures that the cooling water can efficiently absorb and take away heat, while reducing the loss of heat to the external environment. The first sleeve 641 is in direct contact with the water pipe, playing a preliminary protective and heat-insulating role; while the second sleeve 642 further improves the heat insulation effect through the gap between it and the first sleeve 641. This design enables the water temperature adjustment structure 600 to more accurately control the operating temperature of the accelerating tube body 10, extend the service life of the accelerator, and improve the efficiency and stability of the accelerator.

[0058] As a preferred embodiment, one end of the accelerating tube body 10 is sealed and connected to the first drift tube 400 via a first flange 700 , and the other end thereof is sealed and connected to the second drift tube 500 via a second flange 800 .

[0059] During the operation of the accelerator, the electron beam enters the accelerating tube body 10 from the first drift tube 400 through the connection of the first flange 700. In the accelerating tube body 10, the electron beam is accelerated by the high-frequency electromagnetic field and obtains energy gain. Then, the electron beam enters the second drift tube 500 through the connection of the second flange 800 and is finally led out of the accelerator. During the whole process, the flange connection ensures the stable connection and sealing between the accelerating tube body 10 and the drift tube, providing a strong guarantee for the smooth transmission and acceleration of the electron beam.

[0060] As a preferred embodiment, a first pipe joint 410 is provided on the first drifter, the water outlet of the first pipe joint 410 is connected to the first water dividing ring 620, and the water inlet of the first pipe joint 410 is used to communicate with the water outlet of the cooling system;

[0061] The second drifter is provided with a second pipe joint 510, the water inlet end of the second pipe joint 510 is connected to the second water dividing ring 630, and the water outlet end thereof is used to be connected to the water inlet of the cooling system.

[0062] During the operation of the accelerator, the cooling system sends cooling water to the water inlet end of the first pipe joint 410 through its water outlet. The cooling water then flows through the first pipe joint 410, enters the first water distribution ring 620, and is distributed to the spiral water pipe 610. In the spiral water pipe 610, the cooling water exchanges heat with the accelerating tube body 10, absorbs and takes away the heat generated by the accelerating tube body 10. The cooling water that has absorbed the heat then flows into the second water distribution ring 630, and enters the second pipe joint 510 through the water inlet end of the second pipe joint 510. Finally, the cooling water flows out through the water outlet end of the second pipe joint 510 and is sent back to the cooling system for cooling treatment. The cooled water is sent to the first pipe joint 410 again to form a cycle. This connection structure ensures that the cooling water can form a closed-loop circulation, continuously taking away the heat generated by the accelerating tube body 10, thereby effectively controlling the working temperature of the accelerating tube body 10 and extending the service life of the accelerator.

[0063] As a preferred embodiment, the number of accelerating cavities 11 is sixty, among which the cavity 110 of the first accelerating cavity to the third accelerating cavity 110 along the electron beam movement direction is mainly used for bunching, the cavity 110 of the fourth to the seventh accelerating cavity is mainly used for phase sliding, and the cavity 110 of the eighth to the sixtieth accelerating cavity constitutes a light speed segment 112; the cavity 110 of the first accelerating cavity is an input coupling cavity 113, and the cavity 110 of the sixtieth accelerating cavity is an output coupling cavity 114.

[0064] On the basis of the above structure, the electron beam enters the input coupling cavity 113 from one end of the accelerating tube body 10, passes through the cavity 110 of the first accelerating cavity to the cavity 110 of the third accelerating cavity for bunching, and bunches the beam from the electron gun into multiple bunches with shorter phase lengths. Then, the electron beam enters the cavity 110 of the fourth to seventh accelerating cavities for phase adjustment, so that the bunched beam can be exactly located at the peak phase -90° of the sinusoidal wave accelerating electric field when entering the light speed section 112. Finally, the electron beam continues to increase its energy in the light speed section 112, and the accelerated electron beam finally leaves the accelerating tube body 10 smoothly through the output coupling cavity 114, providing a high-quality electron beam source for subsequent experiments or applications. In this way, the utility model realizes efficient electron beam bunching through the design of the phase-changing speed section 111, reduces the energy dispersion of the beam at the outlet of the accelerating tube body 10, ensures that the bunched beam can be exactly located at the peak phase of -90° of the sinusoidal wave accelerating electric field when entering the light speed section 112, and improves the acceleration efficiency.

[0065] As a preferred embodiment, the total length of the accelerating tube body 10 is 2043.054 mm, and the thickness of the fence 20 is 5.5 mm.

[0066] Based on the above structure, a reasonable total length of the accelerating tube 10 can ensure that the electron beam obtains sufficient energy during the acceleration process while maintaining the compactness and cost-effectiveness of the accelerator. An appropriate thickness of the fence 20 can reduce the phase velocity of the electromagnetic field, improve the mechanical strength, facilitate the chamfering of the beam hole 21, and help reduce the breakdown voltage.

[0067] As a preferred implementation, the edge of the beam hole 21 forms an elliptical structure.

[0068] Based on the above structure, the elliptical structure can effectively reduce the ratio of the surface electric field to the acceleration gradient. At the same time, the design of the elliptical structure also helps to reduce the surface electric field strength, reduce the discharge or breakdown phenomenon that may be caused by the high surface electric field, and further improve the stability and reliability of the accelerating tube 100.

[0069] As a preferred embodiment, the ratio of the major axis to the minor axis of the elliptical structure at the edge of the beam hole is 1.8: 1. Preferably, the major axis is 4.95 mm and the minor axis is 2.75 mm.

[0070] On the basis of the above structure, by accurately designing the major axis, minor axis and the ratio of the major axis to the minor axis of the elliptical structure at the edge of the beam hole, the distribution and intensity of the electromagnetic field can be optimized, so that the electron beam is subjected to a more uniform and stable acceleration force during the acceleration process.

[0071] As a preferred embodiment, the apertures of the beam holes 21 of all fences 20 decrease in sequence. As a preferred embodiment, the radius of the cavity 110 of the accelerating cavity of the phase-variable speed section 111 increases in sequence along the moving direction of the electron beam, the radius of the cavity 110 of the first accelerating cavity reaching the optical speed section 112 reaches a maximum value, and the radius of the cavity 110 of the accelerating cavity of the optical speed section 112 decreases in sequence along the moving direction of the electron beam; the length of the cavity 110 of the accelerating cavity of the phase-variable speed section 111 gradually increases along the moving direction of the electron beam, and the length of the cavity 110 of the accelerating cavity of the optical speed section 112 remains unchanged.

[0072] On the basis of the above structure, in the phase-variable speed section 111 , the radius of the cavity 110 of the acceleration cavity gradually increases, and the length also gradually increases, which is helpful for adjusting the phase velocity and maintaining the resonance frequency.

[0073] As a preferred implementation, the phase velocity βp of the RF field in the phase-changing speed section 111 gradually transitions from 0.54 to 1, and the phase velocity βp of the RF field in the light speed section 112 is 1.

[0074] As a preferred implementation, the input coupling cavity 113 is a cylindrical inner cavity structure, the output coupling cavity 114 is a cylindrical inner cavity structure, and the cavity bodies 110 of the remaining acceleration cavities are composed of two symmetrical bowl-shaped inner cavity structures.

[0075] On the basis of the above structure, a cylindrical inner cavity structure is adopted in the input coupling cavity 113 and the output coupling cavity 114 to facilitate power coupling. A bowl-shaped inner cavity structure is adopted in the main part of the accelerating tube body 10. The design of the bowl-shaped inner cavity structure optimizes the distribution of the electromagnetic field by changing the shape and size of the cavity 110 of the accelerating cavity, thereby improving the shunt impedance R and the quality factor Q value. Under the action of the optimized electromagnetic field, the microwave power can be more efficiently converted to the electron beam to achieve the acceleration of the electron beam. Under the condition of obtaining the same energy gain, the heat generated on the wall of the accelerating tube body 10 is reduced due to the reduction of power consumption loss, thereby reducing the cooling pressure of the water cooling system. In summary, this embodiment combines the advantages of the bowl-shaped inner cavity structure and the cylindrical inner cavity structure, adopts a bowl-shaped inner cavity structure in the main part of the accelerating tube body 10, and reasonably sets the phase velocity change of each accelerating structure. While ensuring that the electron beam has good stability and good energy dissipation, it also improves the beam passing efficiency and the utilization efficiency of the radio frequency power; and retains the cylindrical inner cavity structure for power coupling. An example of the comparison of RF parameters between the bowl-shaped inner cavity structure and the conventional structure in the light speed segment, see Table 1 for specific data:

[0076] Table 1

[0077] Structure / Parameters Phase velocity Shunt Impedance Quality Factor Group velocity Decay Constant General structure 0.999 61.23597 13901 0.011872 0.18134 Bowl-shaped inner cavity structure 0.999 63.494 15425 0.014936 0.1299

[0078] Although only certain components and embodiments of the present application have been illustrated and described, many modifications and changes may be conceived by those skilled in the art without actually departing from the scope and spirit of the claims, such as changes in the size, dimensions, structure, shape and proportion of the various elements, mounting arrangements, material usage, color, orientation, etc.

[0079] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A linear accelerator, characterized in that: It includes an accelerating tube, an input coupler oblique waveguide, an output coupler oblique waveguide, a first drift tube, a second drift tube and a water temperature regulating structure; The accelerating tube is composed of a plurality of accelerating cavities and a plurality of fences; each accelerating cavity is welded with a fence to form a complete accelerating structure, and all accelerating structures are welded to form an accelerating tube body, wherein a beam hole is arranged on each fence, so that all accelerating cavities are interconnected to form a complete beam transmission path; wherein the first cavity along the moving direction of the electron beam is an input coupling cavity, and the last cavity along the moving direction of the electron beam is an output coupling cavity; The input coupler oblique waveguide is in communication with the input coupling cavity and is used to introduce external radio frequency power into the accelerator; The output coupler oblique waveguide is in communication with the output coupling cavity and is used to output the remaining microwave power; The first drift tube is in communication with the input coupling cavity, and is used to provide a passage for the electron beam to enter the acceleration cavity; The second drift tube is in communication with the output coupling cavity, and is used to provide a channel for the accelerated electron beam to leave the accelerating cavity; The water temperature regulating structure includes a spiral water pipe, a first water diversion ring, a second water diversion ring and a water pipe jacket; the first water diversion ring is arranged on the first drift tube, and the second water diversion ring is arranged on the second drift tube; the spiral water pipe is coiled on the outer wall of the accelerating tube body, one end of which is connected to the first water diversion ring, and the other end of which is connected to the second water diversion ring; the water pipe jacket is sleeved on the outside of the spiral water pipe.

2. The linear accelerator according to claim 1, characterized in that: The water pipe jacket comprises a first sleeve and a second sleeve, wherein the first sleeve is sleeved on the outside of the spiral water pipe, and the second sleeve is sleeved on the outside of the second sleeve, and a gap is formed between the second sleeve and the first sleeve.

3. The linear accelerator according to claim 1, characterized in that: One end of the accelerating tube body is sealed and connected to the first drift tube via a first flange, and the other end of the accelerating tube body is sealed and connected to the second drift tube via a second flange.

4. The linear accelerator according to claim 1, characterized in that: The first drifter is provided with a first pipe joint, the water outlet end of the first pipe joint is connected with the first water dividing ring, and the water inlet end thereof is used to be connected with the water outlet of the cooling system; The second drifter is provided with a second pipe joint, the water inlet end of the second pipe joint is connected with the second water dividing ring, and the water outlet end thereof is used to be connected with the water inlet of the cooling system.

5. The linear accelerator according to claim 1, characterized in that: The accelerating cavity comprises a phase-changing speed section and a light speed section which are sequentially connected along the moving direction of the electron beam; the phase-changing speed section is used for focusing and phase sliding the electron beam, and the light speed section is used for increasing the energy of the electron beam.

6. The linear accelerator according to claim 5, characterized in that: The number of the accelerating cavities is sixty, among which the cavities of the first accelerating cavity to the third accelerating cavity along the electron beam movement direction are mainly used for bunching, the cavities of the fourth to the seventh accelerating cavities are mainly used for phase sliding, and the cavities of the eighth to the sixtieth accelerating cavities constitute the light speed section; the cavity of the first accelerating cavity is an input coupling cavity, and the cavity of the sixtieth accelerating cavity is an output coupling cavity.

7. The linear accelerator according to claim 6, characterized in that: The edge of the beam hole forms an elliptical structure; the total length of the accelerating chamber is 2043.054 mm, and the thickness of the fence is 5.5 mm; the ratio of the major axis to the minor axis of the elliptical structure at the edge of the beam hole is 1.8:

1.

8. The linear accelerator according to claim 7, characterized in that: The input coupling cavity is a cylindrical inner cavity structure, the output coupling cavity is a cylindrical inner cavity structure, and the cavity bodies of the remaining acceleration cavities are composed of two symmetrical bowl-shaped inner cavity structures.

9. The linear accelerator according to claim 8, characterized in that: The apertures of the beam holes of all fences decrease in sequence; the cavity radius of the accelerating cavity of the phase-changing speed section increases in sequence along the moving direction of the electron beam, the cavity radius of the first accelerating cavity reaching the light speed section reaches a maximum value, and the cavity radius of the accelerating cavity of the light speed section decreases in sequence along the moving direction of the electron beam; the cavity length of the accelerating cavity of the phase-changing speed section increases gradually along the moving direction of the electron beam, and the cavity length of the accelerating cavity of the light speed section remains unchanged.

10. The linear accelerator according to claim 9, characterized in that: The phase velocity βp of the RF field in the phase-changing speed section gradually transitions from 0.54 to 1, and the phase velocity βp of the RF field in the light speed section is 1.

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