Method for preparing radio frequency quadrupole field accelerating cavity assembly through 3D printing

Abstract

The invention belongs to the field of accelerator assembly preparation, and discloses a method for preparing a radio frequency quadrupole field accelerating cavity assembly through 3D printing, distribution and use of copper powder can be more accurately controlled by adopting a selective melting powder laying printing technology, material waste or unnecessary cutting loss in a traditional manufacturing method is avoided, and the manufacturing efficiency is improved. The utilization efficiency of the material is greatly improved. In the electron beam melting forming process, the copper powder can be molten and solidified more evenly, and stress or defects generated by machining on the surface and the interior of a material are reduced. According to the 3D printing technology adopted by the invention, complex geometrical shapes (such as detailed structures of a radio frequency quadrupole field acceleration cavity) can be accurately manufactured in a vacuum environment, and the precise structures are difficult to machine and form at one time in the traditional manufacturing process and need to be machined and assembled for multiple times. In conclusion, through the adoption of the 3D printing and electron beam forming technology, the manufacturing efficiency is improved, and the material waste is reduced.

Description

Technical Field

[0001] The invention belongs to the field of accelerator component preparation, and in particular relates to a method for preparing a radio frequency quadrupole field accelerating cavity component by using 3D printing. Background Art

[0002] The radio frequency quadrupole accelerator (RFQ) is a linear accelerator widely used in the low-energy beam segment and is often used at the front end of a high-current accelerator. This type of accelerator cavity achieves beam focusing, bunching and acceleration through an alternating electric field, and is an important injector for injecting low-energy beams into high-energy accelerators. The design of the RFQ accelerator enables it to effectively convert low-energy ion beams into high-energy density beams and transmit them to the next acceleration stage, which is of great significance to nuclear physics experiments, proton therapy, materials science, and industrial irradiation.

[0003] At present, traditional RFQ accelerators are mostly prepared using a modular manufacturing method. This method divides the acceleration chamber into four independent components, each of which includes a pole head (electrode), which are processed separately and then assembled and fixed to form a complete RFQ acceleration chamber. However, this processing method faces many challenges and limitations. First, the material utilization rate of the modular processing method is low. Due to the low material utilization efficiency of the traditional preparation method, waste is generated during the processing, which increases the material cost. Secondly, the method of separating and processing components and then assembling them makes the processing cycle longer and the processing process more complicated. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned problems of low material utilization and complicated processing flow, and to provide a method for preparing a radio frequency quadrupole field acceleration cavity component by integrated molding using 3D printing.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: A method for preparing a radio frequency quadrupole field acceleration cavity component by 3D printing comprises the following steps: Modeling the radio frequency quadrupole field accelerator and the connecting parts to obtain an initial model; The initial model is enlarged and thickened to obtain a printed model; According to the printed model, in a vacuum environment, electron beam is used to perform selective melting powder printing on the substrate to form a preliminary model of the radio frequency quadrupole field accelerator components and connectors; Separating the preliminary model of the radio frequency quadrupole field accelerator components and connectors from the base plate; The surfaces of the radio frequency quadrupole field accelerator assembly and the connector are ground and polished to make the upper end surface and the lower end surface of the radio frequency quadrupole field accelerator assembly parallel and perpendicular to the central axis, so as to obtain the radio frequency quadrupole field accelerator assembly and the connector of the required size; The radio frequency quadrupole field acceleration components are connected through a connector to obtain a radio frequency quadrupole field acceleration cavity.

[0006] A further improvement of the present invention is that the radio frequency quadrupole accelerator is modeled, and the specific method for obtaining the initial model is as follows: Determine the accelerator geometry based on the accelerator's operating frequency and accelerated particles; According to the accelerator geometry, the geometry of the radio frequency quadrupole field accelerator is modeled to obtain an initial model of the 3D structure.

[0007] A further improvement of the present invention is that the size of the printed model is 1.5% to 2.5% larger than the size of the required radio frequency quadrupole field accelerator, the outer surface thickness of the printed model is 0.15 to 0.45 mm thicker than the outer surface thickness of the required radio frequency quadrupole field accelerator, and the inner surface thickness of the printed model is 0.2 to 0.8 mm thicker than the inner surface thickness of the required radio frequency quadrupole field accelerator.

[0008] A further improvement of the present invention is to design the radio frequency quadrupole accelerator component to be lightweight, such as by adopting a mesh hollow structure.

[0009] A further improvement of the present invention is that, according to the printing model, in a vacuum environment, an electron beam is used to perform selective melting powder printing on a substrate to form a preliminary model of a radio frequency quadrupole field accelerator component and a connector. The specific method is as follows: The printing environment is filled with protective gas and then evacuated. After reaching a predetermined vacuum level, selective melt powder printing is carried out using oxygen-free copper powder as the raw material to form a preliminary model of the radio frequency quadrupole field accelerator components and connectors.

[0010] A further improvement of the present invention is that the vacuum degree of the vacuum environment is 10 -1 Pa level.

[0011] A further improvement of the present invention is that when an electron beam is used to perform selective melting powder printing on a substrate, the electron acceleration voltage of the electron beam printing is 60 kV, the electron beam current is 21 mA, the filling line spacing is 0.1 mm, the printing powder layer thickness is 0.05 mm, the scanning speed is 1.5-4 m / s, and the copper powder is high-purity oxygen-free copper powder with as low an oxygen content as possible, such as oxygen-free copper powder with a particle size of 45-106 μm and a copper content of more than 99.99%.

[0012] A further improvement of the present invention is that when grinding and polishing the surface of the radio frequency quadrupole field accelerator component, a grinder is used to roughly grind the concave and convex parts of the surface of the radio frequency quadrupole field accelerator component, and then sandpaper is used to finely grind the surface of the radio frequency quadrupole field accelerator component, and finally, sandpaper with a mesh size of 1200 or above is used for final grinding to complete the grinding process.

[0013] A further improvement of the present invention is that when grinding and polishing the surface of the radio frequency quadrupole field accelerator component, an abrasive flow polishing method is adopted, and a polymer silicon carbide abrasive is used for polishing in a bidirectional automatic circulation polishing machine. The polishing time is determined by measuring the dimensional error margin, and the polishing process is completed so that both the size and the inner surface roughness meet the requirements.

[0014] A further improvement of the present invention is that the connecting piece is a flange.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention adopts selective melt powder printing technology to more accurately control the distribution and use of copper powder, avoid material waste or unnecessary cutting loss in traditional manufacturing methods, and greatly improve the utilization efficiency of materials. In the electron beam melting and forming process of the present invention, the copper powder can be melted and solidified more evenly, reducing the stress or defects on the surface and inside of the material caused by processing. The 3D printing technology used in the present invention allows complex geometric shapes (such as the detailed structure of the radio frequency quadrupole field acceleration cavity) to be accurately manufactured in a vacuum environment. These precision structures are difficult to process and form in one time during the traditional manufacturing process and require multiple processes for assembly. In summary, the present invention solves the problems of low material utilization and low processing efficiency commonly seen in traditional manufacturing methods by adopting 3D printing and electron beam forming technology, thereby not only improving manufacturing efficiency but also reducing material waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a flow chart of the present invention; Figure 2 This is the result diagram of the dipole mode distribution of a RFQ component tested by the network analyzer; Figure 3 This is another dipole mode distribution result diagram of the RFQ component tested by the network analyzer; Figure 4 This is the result diagram of the quadrupole mode distribution of the RFQ component tested by the network analyzer. DETAILED DESCRIPTION

[0017] In order to further understand the content of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the embodiments are only for explaining the present invention and are not intended to limit it.

[0018] See also Figure 1 A method for preparing a radio frequency quadrupole field acceleration cavity component by 3D printing comprises the following steps: S1, model the radio frequency quadrupole field accelerator and obtain the initial model.

[0019] S2, enlarging and thickening the initial model to obtain a printed model.

[0020] S3, based on the printed model, selective melting powder printing is performed on the substrate using an electron beam in a vacuum environment to form a preliminary model of the radio frequency quadrupole field accelerator components and connectors.

[0021] S4, separate the preliminary model of the radio frequency quadrupole field accelerator components and connectors from the base plate.

[0022] S5, grinding and polishing the surfaces of the radio frequency quadrupole field accelerator assembly and the connector, so that the upper end face and the lower end face of the radio frequency quadrupole field acceleration assembly are parallel and perpendicular to the central axis, and the radio frequency quadrupole field acceleration assembly and the connector of the required size are obtained.

[0023] S6, connecting the radio frequency quadrupole field acceleration components through a connector to obtain a radio frequency quadrupole field acceleration cavity.

[0024] Embodiment 2: The specific method for modeling the radio frequency quadrupole accelerator and obtaining the initial model is as follows: According to the operating frequency of the 3D printer and the accelerated particles, the geometric structure and the pole shape of the accelerator are determined; according to the geometric structure and the pole shape of the accelerator, the geometric structure of the radio frequency quadrupole accelerator is modeled in the CAD modeling software to obtain the initial model of the 3D structure.

[0025] By determining the accelerator geometry based on the operating frequency of the accelerator and the accelerated particles, it can be ensured that the accelerator design meets the actual operating requirements. This modeling method based on physics and technical requirements helps to improve the design accuracy, thereby ensuring the stability and performance of the accelerator when operating at high frequencies. During the modeling process, the operating characteristics of the 3D printer (such as printing accuracy, material properties, thermal deformation during printing, etc.) are taken into account, which helps to solve potential printing problems in the design stage. Through precise modeling, each layer of material in the 3D printing process can be closely matched with the design structure, reducing errors and processing difficulties, and ensuring a smooth printing process. The RF quadrupole field accelerator needs to have very precise geometry and surface finish to ensure the uniform distribution and acceleration effect of the RF field. 3D modeling and printing provide a high degree of freedom and high precision implementation method.

[0026] Embodiment 3: After the metal powder melts and solidifies, the printed part shrinks in size as the temperature gradually decreases. Therefore, the initial 3D model is enlarged in size according to the material thermal expansion conversion, and the allowance is added in advance for the loss caused by grinding, polishing and machining, so that the error in the geometric dimensions of the final sample and the initial design model is minimized. The size of the printed model is 1.5%~2.5% larger than the size of the required RF quadrupole accelerator. The thickness of the outer surface of the printed model is 0.15~0.45mm thicker than the thickness of the outer surface of the required RF quadrupole accelerator, and the thickness of the inner surface of the printed model is 0.2~0.8mm thicker than the thickness of the inner surface of the required RF quadrupole accelerator.

[0027] During the 3D printing process, especially when using electron beam melting molding technology, the material will shrink due to heating. By increasing the size of the initial model, the shrinkage and deformation in this process can be effectively compensated to ensure that the final printed RF quadrupole field accelerator has the correct size and shape. The thickened outer and inner surface thicknesses also help to maintain the required surface quality and structural integrity through grinding and polishing during later processing. The appropriate thickening of the outer and inner surface thicknesses of the initial model can ensure that grinding and polishing can be performed during later processing, removing any rough or uneven areas that may exist during the printing process, and obtaining a flatter and smoother surface. This is critical for the RF quadrupole field accelerator because the surface quality directly affects the distribution of the RF field and the performance of the accelerator.

[0028] Embodiment 4: The radio frequency quadrupole accelerator adopts a lightweight design (such as a mesh hollow structure), which greatly saves the use of raw materials and reduces manufacturing costs while maintaining mechanical strength.

[0029] Embodiment 5: The printed model of this embodiment is a RFQ acceleration chamber assembly of 72.5mm×72.5mm×100mm, which is 1 / 6 of the original model size. The specific implementation steps are as follows: Step 1: Build an accelerating cavity model in the CAD modeling software according to the RFQ accelerating cavity frequency. The accelerating cavity original model acceleration frequency is 162.5 MHz.

[0030] Step 2: Add size scaling and printing polishing allowance to the designed model. Considering the thermal expansion effect of the metal, the model is enlarged by 1.3%~3.5%. Considering the loss caused by grinding and polishing, the outer surface thickening of the model is 0.12~0.5mm, and the inner surface thickening is 0.15~0.7mm.

[0031] Step 3: Input the printed model into the printing equipment, preheat the substrate to 350-500°C, fill it with helium protective gas, and then evacuate it. Repeat the operation to replace the oxygen and other interfering gases in the printing environment, and maintain the vacuum degree at 10 -1 Pa level. Oxygen-free copper powder with a particle size of 45-106 μm was selected for powder spreading. The copper content of oxygen-free copper was above 99.99%. The thickness of the printed powder layer was 0.05 mm, and the spacing between the filling lines was 0.1 mm. During the printing process, the electron acceleration voltage of the electron beam printing was 60 kV, the electron beam current was 21 mA, and the scanning speed was 1.5-4 m / s.

[0032] Step 4: After printing, separate the RFQ acceleration chamber assembly and the substrate, use a small grinder to roughly grind the uneven surface, and then use sandpaper for fine grinding. After grinding, customize the fixture for the model to protect the end face of the specimen and guide the abrasive, place it, and polish it in a two-way automatic cycle polishing machine using high molecular silicon carbide abrasive until the size and finish meet the error requirements, completing the polishing process. Finally, put the assembly into the machining center for cutting, so that the two ends are flat and parallel to each other and perpendicular to the axis, and obtain a complete 3D printed RFQ acceleration chamber assembly.

[0033] Step 5, CST simulation and grid divider frequency measurement were performed on the obtained RFQ accelerating cavity assembly, and the results are shown in Table 1. The results show that the error between the grid divider measured frequency and the frequency obtained by CST simulation is between 0.045% and 0.247%, which meets the error requirements for accelerator preparation. The test and simulation results show that the accelerator properties of the RFQ accelerating cavity assembly prepared by the new 3D printing method can meet the accelerator preparation requirements after the optimization of the preparation process and preparation cost, which proves the advanced nature of this scheme.

[0034] Table 1 Comparison table of simulation frequency and test frequency of radio frequency quadrupole (RFQ) accelerating cavity components

[0035] As can be seen from Table 1, the actual measured frequency is very close to the CST (simulated) frequency, with an error between 0.85 MHz and 11.43 MHz. The relative error values ​​are small, ranging between 0.045% and 0.247%, indicating that the present invention can predict the actual frequency with high accuracy. Table 1 shows that the different operating modes are correctly identified in both simulation and measurement, supporting the effectiveness of the present invention in identifying specific resonant modes. The field distribution of each mode can be visually verified in different diagrams, further supporting the accuracy of the present invention. In summary, the model printed by the present invention is reliable and accurate, and is of great value in predicting the behavior of RFQ accelerating cavity components in actual scenarios.

[0036] The electron beam printing used in the present invention is only one form in the embodiments, and other forms of laser printing can also realize all the methods of the present invention.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a radio frequency quadrupole field acceleration cavity component by 3D printing, characterized in that: The following steps are involved: Modeling the radio frequency quadrupole field accelerator and the connecting parts to obtain an initial model; The initial model is enlarged and thickened to obtain a printed model; According to the printed model, in a vacuum environment, electron beam is used to perform selective melting powder printing on the substrate to form a preliminary model of the radio frequency quadrupole field accelerator components and connectors; Separating the preliminary model of the radio frequency quadrupole field accelerator components and connectors from the base plate; The surfaces of the radio frequency quadrupole field accelerator assembly and the connector are ground and polished to make the upper end surface and the lower end surface of the radio frequency quadrupole field accelerator assembly parallel and perpendicular to the central axis, so as to obtain the radio frequency quadrupole field accelerator assembly and the connector of the required size; The radio frequency quadrupole field accelerating components are connected through a connecting piece to obtain a radio frequency quadrupole field accelerating cavity.

2. The method for preparing a radio frequency quadrupole accelerating cavity component by 3D printing according to claim 1, characterized in that: The specific method for modeling the radio frequency quadrupole accelerator and obtaining the initial model is as follows: Determine the accelerator geometry based on the accelerator's operating frequency and accelerated particles; According to the accelerator geometry, the geometry of the radio frequency quadrupole field accelerator is modeled to obtain an initial model of the 3D structure.

3. The method for preparing a radio frequency quadrupole accelerating cavity component by 3D printing according to claim 1, characterized in that: The size of the printed model is 1.5% to 2.5% larger than the size of the required radio frequency quadrupole accelerator, the outer surface thickness of the printed model is 0.15 to 0.45 mm thicker than the outer surface thickness of the required radio frequency quadrupole accelerator, and the inner surface thickness of the printed model is 0.2 to 0.8 mm thicker than the inner surface thickness of the required radio frequency quadrupole accelerator.

4. The method for preparing a radio frequency quadrupole accelerating cavity component by 3D printing according to claim 1, characterized in that: Lightweight design of components, such as mesh and other hollow structures.

5. The method for preparing a radio frequency quadrupole accelerating cavity component by 3D printing according to claim 1, characterized in that: According to the printed model, in a vacuum environment, an electron beam is used to perform selective melting powder printing on a substrate to form a preliminary model of the RF quadrupole accelerator components and connectors. The specific method is as follows: The printing environment is filled with protective gas and then evacuated. After reaching a predetermined vacuum level, selective melt powder printing is carried out using oxygen-free copper powder as the raw material to form a preliminary model of the radio frequency quadrupole field accelerator components and connectors.

6. A method for preparing a radio frequency quadrupole accelerating cavity component by 3D printing according to claim 1 or 5, characterized in that: The vacuum degree of the vacuum environment is 10 -1 Pa level.

7. A method for preparing a radio frequency quadrupole accelerating cavity assembly by 3D printing according to claim 1 or 5, characterized in that When an electron beam is used for selective melting powder printing on a substrate, the electron acceleration voltage of the electron beam printing is 60 kV, the electron beam current is 21 mA, the filling line spacing is 0.1 mm, the printing powder layer thickness is 0.05 mm, the scanning speed is 1.5~4 m / s, and the copper powder uses high-purity oxygen-free copper powder with the lowest oxygen content possible, such as oxygen-free copper powder with a particle size specification of 45~106 μm and a copper content of more than 99.99%.

8. The method for preparing a radio frequency quadrupole accelerating cavity assembly by 3D printing according to claim 1, characterized in that: When grinding and polishing the surface of the radio frequency quadrupole field accelerator component, use a grinder to roughly grind the concave and convex parts of the surface of the radio frequency quadrupole field accelerator component, use sandpaper to finely grind the surface of the radio frequency quadrupole field accelerator component, and finally use sandpaper with a mesh size of 1200 or above for final grinding to complete the grinding process.

9. The method for preparing a radio frequency quadrupole accelerating cavity component by 3D printing according to claim 1, characterized in that: When grinding and polishing the surface of the radio frequency quadrupole field accelerator component, abrasive flow polishing is adopted, and high molecular silicon carbide abrasive is used for polishing in a bidirectional automatic circulation polishing machine. At the same time, the inner surface size is measured, and the final polishing time is determined according to the error margin, so that both the size and the surface roughness meet the requirements.

10. The method for preparing a radio frequency quadrupole accelerating cavity component by 3D printing according to claim 1, characterized in that: The connecting parts are flanges.

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