Assembly method for a high-precision separation-focusing interdigital drift tube linear accelerator

Abstract

The present invention relates to an assembly method for a high-precision separation-focusing interdigital drift tube linear accelerator. The accelerator comprises: a DTL cavity, comprising a DTL intermediate plate and DTL side cavities located on both sides of the DTL intermediate plate; the DTL intermediate plate comprises an integrally formed drift tube, support rods, a beam, and a T-shaped plate; the lower surface of the T-shaped plate serves as the assembly surface of the DTL; the DTL intermediate plate and the side cavities are machined with cooling water channels and through holes; an assembly base plate, the assembly base plate having positioning pin holes corresponding to the lower surface of the DTL intermediate plate T-shaped plate; the DTL intermediate plate T-shaped plate and the assembly base plate are positioned by pins and fastened to the assembly base plate by bolts; a plurality of DTL cavities are assembled on the assembly base plate to continuously accelerate the beam. In the present invention, the assembly surfaces and positioning pin holes of all DTL drift tube assemblies and T-shaped plates are finely machined by one-time clamping and machining, thereby ensuring the machining accuracy and assembly positioning accuracy of the plurality of DTL cavities.

Description

Technical Field

[0001] The invention relates to an assembly method of a high-precision separation and focusing interdigital drift tube linear accelerator, belonging to the technical field of accelerators. Background Art

[0002] Interdigital drift-tube linear accelerators (ILAs) are a key component of room-temperature proton and heavy-ion accelerators. Due to their compact size at the same frequency and high shunt impedance at low and medium energies, they are the most popular accelerator configuration in the 3-10 MeV / µV range. Evolving from a cylindrical resonant cavity, ILDs employ a series of drift tubes arranged along the axis of the cylindrical cavity, secured to two beams on opposite sides of the cavity via alternating support rods. This creates an interdigital structure, operating in H-mode, hence the name IH-DTL cavity. Depending on their focusing structure and dynamic design, ILDs can be categorized as either Konus (Combined Zero-Phase Acceleration Structure) drift-tube linacs or Alternating Phase Focusing (APF) drift-tube linacs. APF drift-tube linear accelerators primarily provide transverse focusing and defocusing functions by alternating positive and negative synchronization phases at each acceleration gap, eliminating the need for additional transverse focusing magnets. However, this requires complex phase design and control, and the transverse focusing force provided by the gap electric field is weaker than that provided by the magnets. This limits the beam current intensity allowed by APF drift-tube linear accelerators. Therefore, for the acceleration of high-current ion beams, the KONUS drift-tube linear accelerator architecture is commonly used. The KONUS accelerator architecture is divided into three sections based on beam dynamics, separating longitudinal beam bunching, longitudinal acceleration, and transverse focusing. These functions are implemented in different vacuum chamber regions. Longitudinal beam bunching and acceleration are achieved in the electric drift tube assembly region, while transverse beam focusing is achieved within the magnetic drift tube. Each magnetic drift tube typically requires three sets of quadrupole magnets. In low-energy acceleration architectures, due to space charge effects, a magnetic drift tube is often added for every few electric drift tubes to provide bunching.

[0003] Currently, interdigital drift tube linear accelerators are widely used in scientific research, industry, and medicine. There are two common implementation methods:

[0004] One approach integrates multiple sets of electric drift tubes and magnetic drift tubes within a single vacuum chamber. The chamber components are welded together or connected via high-frequency and vacuum sealing media and then bolted together. Ports such as coupler ports, tuner ports, extraction antenna ports, vacuum pump ports, and vacuum gauge ports are welded to the chamber to connect related ancillary equipment and ensure proper operation. This approach offers advantages such as a more compact system structure and facilitates low-level control. However, its disadvantage is that the inlet phases of each set of electric drift tubes are not adjustable. Typically, at low frequencies, the high-frequency performance and field distribution of the chamber are less susceptible to machining, welding errors, and operational perturbations, making this accelerating structure relatively successful. However, for ultra-high-frequency compact accelerators, this approach places high demands on the dimensional and positional accuracy of the entire accelerator. Furthermore, perturbations during operation can significantly affect the field leveling of each set of drift tubes, compromising the accelerator's stable operation.

[0005] The second approach involves packaging each drift tube group into a separate vacuum chamber, each containing 8-10 drift tubes. Quadrupoles are placed between the chambers to focus the beam. The advantage of this approach is that the entrances of each drift tube group are individually phase-scanned, simplifying the accelerator's development and increasing the stability of the entire acceleration system. However, the disadvantage is that each chamber requires its own vacuum and power source, as well as a low-level system, further complicating the system. Furthermore, alignment between the chambers and the magnets relies on a laser tracker, resulting in an error of approximately 0.1 mm.

[0006] For ultra-high frequency cavities, in order to ensure the transmission efficiency of the beam, extremely high requirements are placed on the dimensional accuracy of the cavity, especially the coaxiality requirements for multiple drift tubes and magnets in and between the accelerating cavities, which is required to be ≤50um. It is difficult for a laser tracker to achieve such high-precision alignment. In order to ensure the high-frequency performance of the cavity, the various components of the cavity need to be welded together or connected together through a high-frequency sealing medium. Welding faces the problem of uncontrollable deformation during the welding process, and high-frequency medium sealing faces the problem of uncontrollable sealing gaps. In order to ensure the vacuum sealing of the cavity, stainless steel flanges need to be welded to each port of the cavity. In order to cool the high-frequency heat generated during the operation of the cavity, cooling water channels need to be brazed on the cavity. These all face the problem of difficult-to-control deformation during the welding process. Summary of the Invention

[0007] In response to the above technical problems, the present invention provides an assembly method for a high-precision separation-focusing interdigital drift tube linear accelerator. The core of the method is that the dimensional accuracy and positioning accuracy of multiple DTL cavities are completed during the machining stage, all welding work is completed before fine machining, and no adjustment or correction is required during the assembly process. The position of each DTL cavity is completely fixed by pins and bolts.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A high-precision separation-focusing interdigital drift tube linear accelerator, comprising:

[0010] A DTL cavity, comprising a DTL middle piece and DTL side cavities located on both sides of the DTL middle piece;

[0011] The DTL middle piece includes an integrally formed drift tube, support rods and beams, and the DTL middle piece is processed with cooling water channels and through holes;

[0012] The DTL intermediate piece is fastened to the assembly base plate.

[0013] In the high-precision separation-focusing interdigital drift tube linear accelerator, preferably, both upper and lower ends of the DTL intermediate piece are provided with T-shaped plates integrally formed with the DTL intermediate piece body, and the T-shaped plates are fastened to the assembly base plate.

[0014] In the high-precision separation-focusing interdigital drift tube linear accelerator, preferably, two or more positioning holes are provided on the T-plate.

[0015] In the high-precision separation-focusing interdigital drift tube linear accelerator, preferably, the cross-section of the positioning hole includes a circle, an ellipse, a diamond or a waist shape.

[0016] In the high-precision separation-focusing interdigital drift tube linear accelerator, preferably, the positioning hole comprises a positioning circular pin hole, and the precision error of the positioning circular pin hole is ≤0.01.

[0017] In the high-precision separation-focusing interdigital drift tube linear accelerator, preferably, the positioning holes further include a positioning transverse waist hole and a positioning longitudinal waist hole, and the dimensional accuracy error of the positioning transverse waist hole and the positioning longitudinal waist hole to the beam line is ≤0.02.

[0018] In the high-precision separation-focusing interdigital drift tube linear accelerator, preferably, a sealing groove is provided between the DTL intermediate plate and the two DTL side cavities.

[0019] In the high-precision separation-focusing interdigital drift tube linear accelerator, preferably, the sealing groove is filled with a sealing medium.

[0020] In the high-precision separation-focusing interdigital drift tube linear accelerator, preferably, the sealing medium includes indium wire, high-frequency spring, silver wire or aluminum wire.

[0021] A second aspect of the present invention provides a method for assembling the above-mentioned high-precision separation-focusing interdigital drift tube linear accelerator, characterized by comprising the following steps:

[0022] Processing the cooling water channel on the DTL intermediate plate and welding the external water channel joint;

[0023] The DTL intermediate piece and the T-shaped plate are integrally formed, and the through hole, the positioning round pin hole, the positioning transverse waist hole and the positioning longitudinal waist hole are simultaneously processed on the T-shaped plate;

[0024] The assembly base plate and the positioning pin holes are processed and formed;

[0025] The two DTL side cavities are machined and formed, and at the same time, a through hole adapted to the through hole is machined in the DTL side cavity;

[0026] Filling the sealing medium into the sealing groove between the DTL middle piece and the two DTL side cavities;

[0027] The DTL intermediate piece, the two DTL side cavities and the assembly base plate are positioned by pins and fastened together by bolts to form a high-precision separation-focusing interdigital drift tube linear accelerator.

[0028] The present invention has the following advantages due to the adoption of the above technical solution:

[0029] 1. The core key components of the present invention are no longer subjected to welding operations after fine machining, thereby avoiding the uncertain deformation introduced during the welding process and ensuring the high precision of the core key components, especially the coaxiality of the drift tube assembly.

[0030] 2. In the present invention, the finishing of the drift tube and the finishing of the T-plate assembly surface and assembly pin hole are completed by one clamping process, thereby ensuring the relative position accuracy of the drift tube center line and the assembly surface and assembly pin hole.

[0031] 3. The entire finishing of the assembly surfaces and positioning pin holes of all DTL assembly bases of the present invention is completed by one-time clamping and one-time processing, thereby ensuring the processing accuracy and positioning accuracy of the assembly surfaces of multiple drift tube accelerators. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 An overall schematic diagram of a high-precision separation-focusing interdigital drift tube linear accelerator provided by one embodiment of the present invention;

[0033] Figure 2 A schematic diagram of an assembly base plate in the accelerator provided in this embodiment of the present invention;

[0034] Figure 3A schematic diagram of a DTL cavity in an accelerator provided in this embodiment of the present invention;

[0035] Figure 4 A side view of a DTL intermediate plate in an accelerator provided by this embodiment of the present invention;

[0036] Figure 5 A three-dimensional diagram of a DTL intermediate plate in an accelerator provided by this embodiment of the present invention;

[0037] Figure 6 A schematic diagram of a T-shaped plate provided in this embodiment of the present invention;

[0038] The reference numerals in the figures are as follows:

[0039] 1-DTL cavity; 2-assembly base plate;

[0040] 101-DTL middle piece; 102-DTL side cavity; 103-T-type plate;

[0041] 1011-drift tube; 1012-support rod; 1013-beam; 1014-cooling water channel; 1015-through hole;

[0042] 1031-positioning round pin hole; 1032-positioning horizontal waist hole; 1033-positioning longitudinal waist hole;

[0043] 201-Location pin hole. DETAILED DESCRIPTION

[0044] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by ordinary persons in this field based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0045] Unless otherwise defined, the technical or scientific terms used in the present invention shall have the usual meanings understood by persons of ordinary skill in the field to which the present invention belongs. The words "first", "second", "third", "fourth" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprise" mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

[0046] For ease of description, spatially relative terms may be used herein to describe the relationship of one element or feature relative to another element or feature as shown in the figures, such as "inside," "outside," "inner side," "outer side," "lower," "upper," etc. Such spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures.

[0047] For ultra-high frequency cavities, in order to ensure the transmission efficiency of the beam, extremely high requirements are placed on the dimensional accuracy of the cavity, especially the coaxiality requirements for multiple drift tubes and magnets in and between the accelerating cavities, which are required to be ≤50um. It is difficult for a laser tracker to achieve such high-precision alignment. In order to ensure the high-frequency performance of the cavity, the various components of the cavity need to be welded together or connected together through a high-frequency sealing medium. Welding faces the problem of uncontrollable deformation during the welding process, and high-frequency medium sealing faces the problem of uncontrollable sealing gaps. In order to ensure the vacuum sealing of the cavity, stainless steel flanges need to be welded to each port of the cavity. In order to cool the high-frequency heat generated during the operation of the cavity, cooling water channels need to be brazed on the cavity. These all face the problem of difficult-to-control deformation during the welding process.

[0048] Based on the above technical problems, the present invention provides a high-precision separation-focusing interdigital drift tube linear accelerator and an assembly method thereof. The core of the present invention is that the dimensional accuracy and positioning accuracy of multiple DTL cavities are completed during the processing stage, all welding work is completed before fine processing, and no adjustment or correction is required during the assembly process. The position of each DTL cavity is completely fixed by pins and bolts.

[0049] like Figure 1 、 2 As shown in Figures 3 and 4, the high-precision separation-focusing interdigital drift tube linear accelerator involved in the present invention includes: a DTL cavity 1, the DTL cavity 1 includes a DTL intermediate piece 101 and a DTL side cavity 102 located on both sides of the DTL intermediate piece 101; the DTL intermediate piece 101 includes an integrally formed drift tube 1011, a support rod 1012 and a beam 1013, and a cooling water channel 1014 and a through hole 1015 are processed on the DTL intermediate piece 101; an assembly base plate 2, and the DTL intermediate piece 101 is fastened to the assembly base plate 2.

[0050] Further, if Figure 5 、 6As shown, T-shaped plates 103, integrally formed with the DTL intermediate plate 101, are provided at both the upper and lower ends. These plates 103 are securely connected to the assembly base 2. Preferably, the T-shaped plates 103 are provided with two or more positioning holes, each with a circular, elliptical, diamond-shaped, or waist-shaped cross-section. More preferably, the positioning holes include a circular positioning pin hole 1031, a transverse positioning waist hole 1032, and a longitudinal positioning waist hole 1033.

[0051] Furthermore, if Figure 6 As shown, the cross-section of the positioning circular pin hole 1031 in the YZ plane is circular, while the cross-sections of the positioning transverse waist hole 1032 and the positioning longitudinal waist hole 1033 are waist-shaped. The dimensional accuracy error of the positioning circular pin hole 1031 is ≤0.01. The dimensional accuracy error of the positioning transverse waist hole 1032 and the positioning longitudinal waist hole 1033 relative to the beam line is ≤0.02.

[0052] Furthermore, if Figure 3 As shown, a sealing groove is provided between the DTL middle plate 101 and the two DTL side cavities 102. The sealing groove is filled with a sealing medium, which includes an indium wire, a high-frequency spring, a silver wire or an aluminum wire.

[0053] A second aspect of the present invention provides a method for assembling a high-precision separation-focusing interdigital drift tube linear accelerator, comprising the following steps:

[0054] A cooling water channel 1014 is machined on the DTL intermediate plate 101;

[0055] The DTL intermediate piece 101 and the T-shaped plate 103 are integrally formed, and a through hole 1015, a positioning round pin hole 1031, a positioning transverse waist hole 1032 and a positioning longitudinal waist hole 1033 are processed on the T-shaped plate 103;

[0056] The assembly base plate 2 and the positioning pin hole 201 are processed and formed;

[0057] Two DTL side cavities 102 are machined and formed, and at the same time, through holes that match the through holes 1015 are machined in the DTL side cavities 102;

[0058] Fill the sealing groove between the DTL middle piece 101 and the two DTL side cavities 102 with a sealing medium;

[0059] The DTL intermediate piece 101, the two DTL side cavities 102 and the assembly base plate 2 are positioned by pins and fastened together by bolts to form a high-precision separation-focusing interdigital drift tube linear accelerator.

[0060] The DTL chamber 1 of the present invention utilizes a sandwich structure. Its core components are integrally formed using a process called a drift tube 1011, support rods 1012, beam 1013, and T-plate 103. This allows for coaxiality of ≤20 μm. The cooling water channel 1014 on the drift tube 1011 is welded prior to finishing. Simultaneously with the welding of the cooling water channel 1014, a stainless steel pinhole bushing is welded to the support surface of the lower T-plate 103 of the drift tube 1011. The lower support surface of the T-plate 103 serves as the assembly surface. Taking the beam axis of the drift tube 1011 as the reference, the lower surface of the T-plate 103 and the positioning pin holes on the lower surface are finely machined. The pin holes fall on the stainless steel bushing. This process and the fine machining of the inner hole of the drift tube 1011 are fixed and processed in one step. The position accuracy of the lower surface of the T-plate 103 to the beam center of the drift tube 1011 constrains the translational freedom of the DTL cavity 1 along the Y direction. There are three pin holes on the lower surface of the T-plate 103. One pin hole is on the YZ plane and has a circular cross section. The positions of the other two pin holes are as follows: Figure 6 As shown, the cross section is waist-shaped; the dimensional accuracy error of the two pin holes in the Z direction is ≤0.01, and the dimensional accuracy error from the waist-shaped hole to the beam line is ≤0.02; these two pin holes constrain the translational freedom of the DTL cavity 1 along the X and Z directions and the rotational freedom around the Y and Z axes; the lower bottom surface of the T-plate 103 and the assembly surface of the assembly base plate 2 are positioned through the pin holes; the planar contact constrains the rotational freedom of the DTL cavity 1 around the X axis; the drift tube 1011 and the DTL side cavities 102 on both sides (such as Figure 3 A high-frequency sealing groove is provided between the two components (as shown) and filled with a sealing medium. Bolts secure the components together to provide both a high-frequency and vacuum seal. This prevents uncontrolled deformation of the machined components during welding, thereby maintaining the coaxiality of the drift tube 1011 within 20 μm. The assembly reference surface is located on the lower surface of the T-shaped plate 103, which is integrally formed with the drift tube 1011. Therefore, the press-fit gap of the high-frequency sealing medium does not affect the overall assembly accuracy. Frequency deviation caused by the press-fit gap of the high-frequency sealing medium can be mitigated by the tuner configured on each DTL.

[0061] To achieve the aforementioned objectives, the present invention achieves both machining and positioning accuracy for the DTL chamber 1 during the machining phase. The finish machining of the drift tube 1011 and the finish machining of the assembly surfaces and assembly pin holes on the T-plate 103 are completed in a single clamping process. The entire finish machining of all assembly surfaces and positioning pin holes on the assembly base plate 2 is accomplished through a single clamping and machining process. After all of the aforementioned finishing is completed, only necessary cleaning and assembly are performed, without any further heat treatment. All welding and heat treatment are completed prior to finishing. During assembly, the position of the DTL chamber 1 is completely fixed by pins and bolts, constraining its six degrees of freedom: translational freedom along the X, Y, and Z directions, and rotational freedom along the X, Y, and Z axes (X represents the horizontal direction, Y represents the vertical direction, and Z represents the beam direction). Bolts are then used to secure the DTL chamber 1, achieving high-precision system assembly.

[0062] 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for assembling a high-precision separation-focusing interdigital drift tube linear accelerator, wherein the linear accelerator comprises: A DTL cavity (1), the DTL cavity (1) comprising a DTL middle piece (101) and DTL side cavities (102) located on both sides of the DTL middle piece (101); the DTL middle piece (101) comprising an integrally formed drift tube (1011), a support rod (1012) and a beam (1013); a cooling water channel (1014) and a through hole (1015) are machined on the DTL middle piece (101); an assembly base plate (2), the DTL middle piece (101) being fastened to the assembly base plate (2); The upper and lower ends of the DTL intermediate piece (101) are both provided with T-shaped plates (103) integrally formed with the body of the DTL intermediate piece (101), and the T-shaped plates (103) are tightly connected to the assembly base plate (2); The T-shaped plate (103) is provided with two or more positioning holes; the positioning holes include a positioning round pin hole (1031), and the positioning holes also include a positioning transverse waist hole (1032) and a positioning longitudinal waist hole (1033); A sealing groove is provided between the DTL middle piece (101) and the two DTL side cavities (102), and the sealing groove is filled with a sealing medium; It is characterized by comprising the following steps: Processing the cooling water channel (1014) on the DTL intermediate plate (101) and welding external water channel joints; The DTL intermediate piece (101) and the T-shaped plate (103) are integrally formed, and the through hole (1015), the positioning circular pin hole (1031), the positioning transverse waist hole (1032) and the positioning longitudinal waist hole (1033) are simultaneously formed on the T-shaped plate (103); the assembly base plate (2) and the positioning pin hole (201) are also formed; The two DTL side cavities (102) are machined and formed, and a through hole adapted to the through hole (1015) is machined in the DTL side cavity (102); Filling the sealing medium into the sealing groove between the DTL middle piece (101) and the two DTL side cavities (102); The DTL intermediate piece (101), the two DTL side cavities (102) and the assembly base plate (2) are positioned using pins and fastened together by bolts to form a high-precision separation-focusing interdigital drift tube linear accelerator.

2. The assembly method of the high-precision separation-focusing interdigital drift tube linear accelerator according to claim 1, characterized in that: The cross section of the positioning hole includes a circle, an ellipse, a diamond or a waist shape.

3. The assembly method of the high-precision separation-focusing interdigital drift tube linear accelerator according to claim 1, characterized in that: The precision error of the positioning circular pin hole (1031) is ≤0.

01.

4. The assembly method of the high-precision separation-focusing interdigital drift tube linear accelerator according to claim 1, characterized in that: The dimensional accuracy error between the positioning transverse waist hole (1032) and the positioning longitudinal waist hole (1033) and the beam line is ≤0.

02.

5. The assembly method of the high-precision separation-focusing interdigital drift tube linear accelerator according to claim 1, characterized in that: The sealing medium includes indium wire, high-frequency spring, silver wire or aluminum wire.

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