A method for preparing radio frequency quadrupole accelerating cavity components using 3D printing

Abstract

This invention belongs to the field of accelerator component fabrication and discloses a method for fabricating radio frequency quadrupole accelerator cavity components using 3D printing. By employing selective melting powder spreading printing technology, this invention enables more precise control over the distribution and use of copper powder, avoiding material waste or unnecessary cutting losses in traditional manufacturing methods, and greatly improving material utilization efficiency. During the electron beam melting and forming process, the copper powder melts and solidifies more uniformly, reducing stress or defects on the material surface and inside the material caused by processing. The 3D printing technology used in this invention allows for the precise fabrication of complex geometries (such as the detailed structure of radio frequency quadrupole accelerator cavities) in a vacuum environment. These precision structures are difficult to fabricate in a single step in traditional manufacturing processes and require multiple processing steps for assembly. In summary, this invention, by employing 3D printing and electron beam forming technologies, not only improves manufacturing efficiency but also reduces material waste.

Description

Technical Field

[0001] This invention belongs to the field of accelerator component fabrication, specifically relating to a method for fabricating radio frequency quadrupole accelerator cavity components using 3D printing. Background Technology

[0002] A radio frequency quadrupole (RFQ) accelerator is a linear accelerator widely used in the low-energy beam stage, often at the front end of high-current accelerators. This accelerator cavity uses an alternating electric field to focus, concentrate, and accelerate the beam, making it a crucial 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 propagate them to the next acceleration stage, which is of great significance for fields such as nuclear physics experiments, proton therapy, materials science, and industrial irradiation.

[0003] Currently, traditional RFQ accelerators are mostly fabricated using modular manufacturing methods. This method divides the accelerator cavity into four independent components, each including an electrode. These components are fabricated separately and then assembled and fixed together to form a complete RFQ accelerator cavity. However, this fabrication method faces many challenges and limitations. First, the modular fabrication method has low material utilization. Due to the low material utilization efficiency of traditional fabrication methods, waste is generated during processing, increasing material costs. Second, the process of separating and then assembling the components lengthens the processing cycle and complicates the process. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of low material utilization and complex processing procedures mentioned above, and to provide a method for fabricating radio frequency quadrupole accelerator cavity components using 3D printing in an integrated manner.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for fabricating radio frequency quadrupole accelerator cavity components using 3D printing includes the following steps:

[0007] The radio frequency quadrupole accelerator and its connectors were modeled to obtain an initial model;

[0008] The initial model is enlarged and thickened to obtain the printed model;

[0009] Based on the printing model, in a vacuum environment, selective melting powder printing is performed on the substrate using an electron beam to form a preliminary model of the radio frequency quadrupole accelerator components and connectors.

[0010] The preliminary model of the radio frequency quadrupole accelerator components and connectors is separated from the substrate;

[0011] The surfaces of the radio frequency quadrupole accelerator assembly and connectors are ground and polished to make the upper and lower end faces of the radio frequency quadrupole accelerator assembly parallel and perpendicular to the central axis, so as to obtain the radio frequency quadrupole accelerator assembly and connectors of the required size.

[0012] The radio frequency quadrupole acceleration components are connected by connectors to obtain the radio frequency quadrupole acceleration cavity.

[0013] A further improvement of this invention lies in the following method for modeling the radio frequency quadrupole accelerator to obtain the initial model:

[0014] The accelerator geometry is determined based on the accelerator's operating frequency and the accelerated particles.

[0015] Based on the accelerator geometry, the geometry of the radio frequency quadrupole accelerator is modeled to obtain an initial 3D model.

[0016] 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 accelerator, the outer surface thickness of the printed model is increased by 0.15 to 0.45 mm relative to the outer surface thickness of the required radio frequency quadrupole accelerator, and the inner surface thickness of the printed model is increased by 0.2 to 0.8 mm relative to the inner surface thickness of the required radio frequency quadrupole accelerator.

[0017] A further improvement of the present invention is that the radio frequency quadrupole accelerator components are designed to be lightweight, such as by adopting a mesh-like hollow structure.

[0018] A further improvement of this invention lies in that, based on the printing model, in a vacuum environment, selective melting and powder-spreading printing with an electron beam is used on a substrate to form a preliminary model of the radio frequency quadrupole accelerator assembly and connectors. The specific method is as follows:

[0019] The printing environment is filled with protective gas and then evacuated to a predetermined vacuum level. Selective melting and powder coating printing is then performed using oxygen-free copper powder as raw material to form a preliminary model of the radio frequency quadrupole accelerator components and connectors.

[0020] A further improvement of this invention is that the vacuum level of the vacuum environment is 10. -1 Pa level.

[0021] A further improvement of this invention is that, when selectively melting and spreading powder on a substrate using an electron beam, the electron beam printing electron acceleration voltage is 60kV, the electron beam current is 21mA, the fill line spacing is 0.1mm, the powder layer thickness is 0.05mm, the scanning speed is 1.5~4m / s, and the copper powder used is high-purity oxygen-free copper powder with the lowest possible oxygen content, such as oxygen-free copper powder with a particle size of 45~106μm and a copper content of 99.99% or higher.

[0022] A further improvement of the present invention is that, when polishing the surface of the radio frequency quadrupole accelerator assembly, a polisher is used to coarsely polish the uneven areas of the surface of the radio frequency quadrupole accelerator assembly, then sandpaper is used to finely polish the surface of the radio frequency quadrupole accelerator assembly, and finally, sandpaper of 1200 grit or higher is used for final polishing to complete the polishing process.

[0023] A further improvement of this invention is that, when polishing the surface of the radio frequency quadrupole accelerator assembly, an abrasive flow polishing method is used, and high-molecular silicon carbide abrasive is used in a bidirectional automatic circulating polishing machine. The polishing time is determined by measuring the dimensional error margin, and the polishing process is completed, so that the dimensions and the inner surface roughness meet the requirements at the same time.

[0024] A further improvement of the present invention is that the connecting part is a flange.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention employs selective fusion powder-layout printing technology, enabling more precise control over the distribution and use of copper powder. This avoids material waste and unnecessary cutting losses common in traditional manufacturing methods, significantly improving material utilization efficiency. During the electron beam melting and forming process, the copper powder melts and solidifies more uniformly, reducing stress or defects on the material surface and within the material caused by processing. The 3D printing technology used in this invention allows for the precise fabrication of complex geometries (such as the detailed structures of radio frequency quadrupole accelerator cavities) in a vacuum environment. These precision structures are difficult to fabricate in a single step in traditional manufacturing processes, requiring multiple processing steps for assembly. In summary, this invention, by employing 3D printing and electron beam forming technologies, solves the common problems of low material utilization and low processing efficiency in traditional manufacturing methods, thereby not only improving manufacturing efficiency but also reducing material waste. Attached Figure Description

[0027] Figure 1 This is a flowchart of the present invention;

[0028] Figure 2 The diagram shows the mode distribution of a diode in an RFQ component tested by a network analyzer.

[0029] Figure 3 The diagram shows the mode distribution results of another diode component tested by the network analyzer.

[0030] Figure 4 The image shows the results of testing a quadrature mode distribution of an RFQ component using a network analyzer. Detailed Implementation

[0031] To further understand the content of this invention, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the invention.

[0032] See also Figure 1 A method for fabricating radio frequency quadrupole accelerator cavity components using 3D printing includes the following steps:

[0033] S1, Model the radio frequency quadrupole accelerator to obtain the initial model.

[0034] S2, enlarge and thicken the initial model to obtain the printed model.

[0035] S3. Based on the printing model, in a vacuum environment, selective melting powder printing is performed on the substrate using an electron beam to form a preliminary model of the radio frequency quadrupole accelerator components and connectors.

[0036] S4, Separate the preliminary model of the radio frequency quadrupole accelerator components and connectors from the substrate.

[0037] S5. Polish the surface of the RF quadrupole accelerator assembly and connectors to make the upper and lower surfaces of the RF quadrupole accelerator assembly parallel and perpendicular to the central axis, thus obtaining the RF quadrupole accelerator assembly and connectors of the required size.

[0038] S6 connects the RF quadrupole acceleration component through the connector to obtain the RF quadrupole acceleration cavity.

[0039] Example 2:

[0040] The specific method for modeling the radio frequency quadrupole accelerator to obtain the initial model is as follows:

[0041] Based on the operating frequency of the 3D printer and the accelerating particles, the geometry and tip shape of the accelerator are determined. Based on the geometry and tip shape of the accelerator, the geometry of the radio frequency quadrupole accelerator is modeled in CAD modeling software to obtain the initial model of the 3D structure.

[0042] By determining the accelerator geometry based on its operating frequency and the accelerated particles, it's possible to ensure the accelerator design meets actual operational requirements. This modeling approach, based on physics and technical needs, helps improve design accuracy, thereby ensuring the accelerator's stability and performance during high-frequency operation. The modeling process considers the operating characteristics of the 3D printer (such as printing accuracy, material properties, and thermal deformation during printing), helping to address potential printing problems at the design stage. Precise modeling ensures that each layer of material in the 3D printing process closely matches the designed structure, reducing errors and processing difficulties, and ensuring a smooth printing process. Radio frequency quadrupole accelerators require highly precise geometry and surface finish to guarantee a uniform distribution of the radio frequency field and effective acceleration; 3D modeling and printing provide a high degree of freedom and high precision for achieving this.

[0043] Example 3:

[0044] As the metal powder melts and solidifies, the printed part shrinks in size as the temperature gradually decreases. Therefore, the initial 3D model is enlarged based on the thermal expansion of the material, and allowances are added in advance to account for losses from grinding, polishing, and machining, minimizing the geometrical error between the final sample and the initial design model. The size of the printed model is 1.5% to 2.5% larger than the required size of the RF 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 RF quadrupole accelerator, and the inner surface thickness is 0.2 to 0.8 mm thicker than the inner surface thickness of the required RF quadrupole accelerator.

[0045] During 3D printing, especially when using electron beam melting technology, materials shrink due to heating. Increasing the size of the initial model effectively compensates for this shrinkage and deformation, ensuring the final printed radio frequency quadrupole accelerator has the correct size and shape. The increased thickness of the outer and inner surfaces also helps maintain the required surface quality and structural integrity through grinding and polishing during later processing. Appropriately increasing the thickness of the outer and inner surfaces of the initial model ensures that grinding and polishing can be performed later to remove any rough or uneven areas that may have been present during the printing process, resulting in a smoother and more even surface. This is crucial for radio frequency quadrupole accelerators because surface quality directly affects the distribution of the radio frequency field and the accelerator's performance.

[0046] Example 4:

[0047] The radio frequency quadrupole accelerator adopts a lightweight design (such as a mesh-like hollow structure), which greatly saves raw materials and reduces manufacturing costs while maintaining mechanical strength.

[0048] Example 5:

[0049] The printed model in this embodiment is an RFQ acceleration cavity assembly measuring 72.5mm × 72.5mm × 100mm, which is 1 / 6 the size of the original model. The specific implementation steps are as follows:

[0050] Step 1: Construct an acceleration cavity model in CAD modeling software based on the RFQ acceleration cavity frequency. In this case, the original acceleration cavity model is selected with an acceleration frequency of 162.5MHz.

[0051] Step 2: Add size scaling and printing / polishing allowance to the designed model. Considering the thermal expansion effect of metal, enlarge the model by 1.3%~3.5%. Considering the loss caused by grinding and polishing, the thickness of the outer surface of the model is 0.12~0.5mm, and the thickness of the inner surface is 0.15~0.7mm.

[0052] Step 3: Input the printing model into the printing equipment, preheat the substrate to 350~500℃, fill with helium protective gas, then evacuate the vacuum. Repeat this process to displace interfering gases such as oxygen from the printing environment, maintaining a vacuum level of 10. -1 Pa level. Oxygen-free copper powder with a particle size of 45~106μm was selected for powder spreading. The copper content of oxygen-free copper was above 99.99%. The powder layer thickness was 0.05mm, the filling line spacing was 0.1mm, and the electron beam printing acceleration voltage was 60kV, the electron beam current was 21mA, and the scanning speed was 1.5~4m / s.

[0053] Step four: After printing, separate the RFQ accelerator cavity assembly from the substrate. Use a small grinder to roughen the uneven surfaces, followed by fine sanding with sandpaper. After sanding, use a custom-made fixture to protect the end face of the specimen and guide the abrasive. Place it in a bidirectional automatic circulating polishing machine using high-polymer silicon carbide abrasive until the dimensions and surface finish meet the tolerance requirements, completing the polishing process. Finally, place the assembly in a machining center for cutting to ensure that both ends are flat, parallel, and perpendicular to the axis, resulting in a complete 3D printed RFQ accelerator cavity assembly.

[0054] Step five involves performing CST simulation and frequency measurement using a network analyzer on the obtained RFQ accelerator cavity assembly. The results are shown in Table 1. The results indicate that the error between the frequency measured by the network analyzer and the frequency obtained through CST simulation is between 0.045% and 0.247%, which meets the error requirements for accelerator fabrication. The test and simulation results demonstrate that the accelerator properties of the RFQ accelerator cavity assembly fabricated using this novel 3D printing method, after optimization in fabrication process and cost, meet the requirements for accelerator fabrication, proving the advancement of this approach.

[0055] Table 1 Comparison of Simulated and Test Frequencies for Radio Frequency Quadrupole (RFQ) Accelerator Cavity Components

[0056]

[0057] As shown in Table 1, the actual measured frequency is very close to the CST (simulated) frequency, with an error ranging from 0.85 MHz to 11.43 MHz. The relative error values ​​are small, between 0.045% and 0.247%, indicating that the present invention can predict the actual frequency with high accuracy. Table 1 shows that different operating modes were correctly identified in both simulation and measurement, supporting the effectiveness of the present invention in identifying specific resonance modes. The field distribution of each mode can be visually verified in different illustrations, further supporting the accuracy of the present invention. In conclusion, the model printed by the present invention is reliable and accurate, and has significant value for predicting the behavior of RFQ accelerating cavity components in real-world scenarios.

[0058] The use of electron beam printing in this invention is only one embodiment; other methods of laser printing can also achieve all the methods of this invention.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do 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 fabricating a radio frequency quadrupole acceleration cavity assembly using 3D printing, characterized in that, Includes the following steps: The components and connectors of the radio frequency quadrupole accelerator were modeled to obtain an initial model; The initial model is enlarged and thickened to obtain the printed model; 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 increased by 0.15 to 0.45 mm relative to the outer surface thickness of the required radio frequency quadrupole accelerator, and the inner surface thickness of the printed model is increased by 0.2 to 0.8 mm relative to the inner surface thickness of the required radio frequency quadrupole accelerator. Based on the printing model, in a vacuum environment, selective melting powder spreading printing is performed on the substrate using an electron beam to form the initial blank of the radio frequency quadrupole accelerator assembly and connectors. When selective melting powder spreading printing is performed on the substrate using an electron beam, the electron acceleration voltage is 60kV, the electron beam current is 21mA, the fill line spacing is 0.1mm, the powder layer thickness is 0.05mm, the scanning speed is 1.5~4m / s, and the copper powder used is high-purity oxygen-free copper powder with a particle size of 45~106μm and a copper content of over 99.99%. Separate the blanks of the radio frequency quadrupole accelerator components and connectors from the substrate; The surface of the initial blank of the radio frequency quadrupole accelerator assembly and connector is ground and polished to make the upper and lower end faces of the radio frequency quadrupole accelerator assembly parallel and perpendicular to the central axis, so as to obtain the radio frequency quadrupole accelerator assembly and connector of the required size. The radio frequency quadrupole accelerator components are connected by connectors to obtain the radio frequency quadrupole accelerator cavity.

2. The method for fabricating a radio frequency quadrupole acceleration cavity assembly using 3D printing according to claim 1, characterized in that, The specific method for modeling the radio frequency quadrupole accelerator components to obtain the initial model is as follows: The accelerator geometry is determined based on the accelerator's operating frequency and the accelerated particles. Based on the accelerator geometry, the geometry of the radio frequency quadrupole accelerator is modeled to obtain an initial 3D model.

3. The method for fabricating a radio frequency quadrupole acceleration cavity assembly using 3D printing according to claim 1, characterized in that, Based on the printing model, the specific method for forming the initial blank of the radio frequency quadrupole accelerator assembly and connectors by selectively melting and spreading powder on the substrate using an electron beam in a vacuum environment is as follows: The printing environment is filled with protective gas and then evacuated to a predetermined vacuum level. Selective melting and powder spreading printing is then performed using oxygen-free copper powder as raw material to form the initial blank of the radio frequency quadrupole accelerator assembly and connector.

4. A method for fabricating a radio frequency quadrupole acceleration cavity assembly using 3D printing according to claim 1 or 3, characterized in that, The vacuum level of the vacuum environment is 10. -1 Pa level.

5. The method for fabricating a radio frequency quadrupole acceleration cavity assembly using 3D printing according to claim 1, characterized in that, When polishing the surface of the RF quadrupole accelerator component blank, a grinder is used to coarsely grind the uneven areas on the surface of the RF quadrupole accelerator component blank, sandpaper is used to finely grind the surface of the RF quadrupole accelerator component blank, and finally, sandpaper of 1200 grit or higher is used for final polishing to complete the polishing process.

6. The method for fabricating a radio frequency quadrupole acceleration cavity assembly using 3D printing according to claim 1, characterized in that, When polishing the surface of the initial blank of the radio frequency quadrupole accelerator component, the abrasive flow polishing method is adopted. High molecular silicon carbide abrasive is used for polishing in a bidirectional automatic circulating polishing machine. At the same time, the inner surface dimensions are measured, and the final polishing time is determined according to the error margin, so that the dimensions and surface roughness meet the requirements at the same time.

7. A method for fabricating a radio frequency quadrupole acceleration cavity assembly using 3D printing according to claim 1, characterized in that, Flanges are used for the connections.

Images