Drift tube type linear accelerator

Abstract

The invention relates to the technical field of ion accelerators, in particular to a drift tube type linear accelerator. The linear accelerator comprises a cavity cylinder which is arranged to be of a shell structure with a cavity inside; the drift tube is a square tube of which the two ends are provided with open slots; the first cross beam and the second cross beam are arranged in the cavity; wherein the plurality of drift tubes are arranged at intervals in the cavity along the central axis of the cavity cylinder, the first cross beam and the second cross beam are both provided with supporting rods, and the supporting rods on the first cross beam and the second cross beam are alternately arranged and are connected with the drift tubes in a one-to-one correspondence manner; the first cross beam is connected with the positive electrode, and the second cross beam is connected with the negative electrode, so that a radio frequency electric field is established between the adjacent drift tubes. According to the linear accelerator, the drift tube is arranged to be the square tubes with the opening grooves in the two ends, and the square tubes are arranged in a mixed mode, so that the linear accelerator can keep a high acceleration gradient in the longitudinal direction and can have high focusing force in the transverse direction.

Description

Technical Field

[0001] This invention relates to the field of ion accelerator technology, and in particular to a drift tube linear accelerator. Background Technology

[0002] Drift tube linear accelerators (DTLs) are a commonly used type of linear accelerator. Their core structure consists of hollow cylinders with specific lengths and inner and outer diameters arranged at specific gaps. A radio frequency electric field is established between two adjacent hollow cylinders for the longitudinal acceleration and focusing of protons or heavy ions.

[0003] However, the electric field generated by this structure cannot simultaneously meet the requirements for both lateral and longitudinal beam propagation. To increase the lateral focusing force of the electric field, researchers have considered many methods, such as changing the acceleration phase to sacrifice longitudinal acceleration and beam focusing performance to obtain the lateral focusing force, or installing magnetic focusing elements in the cavity. However, these methods would lead to a decrease in the acceleration gradient of the accelerator, an increase in power consumption, and an increase in the cavity size, which would greatly increase the stability of the accelerator as well as the production, operation, and maintenance costs. Summary of the Invention

[0004] This invention aims to solve the technical problems existing in related technologies. To this end, this invention proposes a drift tube type linear accelerator, which optimizes the acceleration structure of the linear accelerator by adopting a combination of semi-open square drift tubes, so as to ensure that the accelerator has both a high acceleration gradient and a strong lateral focusing force.

[0005] This invention provides a drift tube linear accelerator, comprising: The cavity tube is designed as a shell structure with an internal cavity. The drift tube is a square tube with open slots at both ends; The first crossbeam is installed at the upper part of the cavity; The second crossbeam is installed at the lower part of the cavity; Among them, a plurality of drift tubes are arranged at intervals along the central axis of the cavity. Both the first crossbeam and the second crossbeam are provided with support rods. The support rods on the first crossbeam and the second crossbeam are arranged alternately and connected to the drift tubes one by one. The first crossbeam is connected to the positive electrode, and the second crossbeam is connected to the negative electrode, for establishing a radio frequency electric field between adjacent drift tubes; The drift tube includes a first drift tube for laterally focusing the beam; One end of the first drift tube has a notch on its horizontal sidewall, and the other end of the first drift tube has a notch on its vertical sidewall, so that the two ends of the first drift tube form openings with different extending directions. The drift tube also includes a second drift tube for focusing and defocusing conversion. The second drift tube has notches at both ends of its horizontal sidewall or at both ends of its vertical sidewall, so that the two ends of the second drift tube form openings with the same extension direction.

[0006] According to the present invention, in a drift tube type linear accelerator, the length of the drift tube gradually increases from one end of the cavity to the other end of the cavity.

[0007] According to the present invention, in a drift tube type linear accelerator, any two adjacent drift tubes are positioned with their opening slots extending in different directions as opposite ends.

[0008] According to the present invention, a drift tube type linear accelerator is provided in which the first drift tube is disposed in the cavity in two postures: one is that the end of the first drift tube extending vertically with an open groove faces the left end of the cavity, and the other is that the end of the first drift tube extending horizontally with an open groove faces the left end of the cavity.

[0009] According to the present invention, a drift tube type linear accelerator is provided in which a plurality of first drift tubes are arranged in the same orientation to superimpose focusing intensity in a set direction corresponding to the orientation.

[0010] According to the present invention, a drift tube type linear accelerator is provided, wherein the second drift tube is disposed between two first drift tubes with different attitudes to form a periodic FODO focusing structure.

[0011] According to the present invention, a drift tube linear accelerator is provided in which the first crossbeam and the second crossbeam extend from the left end of the cavity to the right end of the cavity and are symmetrically distributed relative to the central axis of the cavity.

[0012] According to the present invention, a drift tube linear accelerator is provided with beam holes for connecting the inside and outside of the cavity at both end faces of the cavity, and the central axis of the beam holes coincides with the central axis of the cavity.

[0013] The above-described one or more technical solutions of this invention have at least one of the following technical effects: By setting the drift tube as a square tube and setting open slots at both ends to form a semi-open square drift tube, and by mixing and arranging the square drift tubes, the linear accelerator can maintain a high acceleration gradient in the longitudinal direction and have a strong focusing force in the transverse direction, thereby shortening the length of the linear accelerator and improving the quality of the extracted beam and the transmission efficiency of the linear accelerator.

[0014] In addition to the technical problems solved by the present invention, the technical features of the technical solutions constituted by the present invention, and the advantages brought about by the technical features of these technical solutions as described above, other technical features of the present invention and the advantages brought about by these technical features will be further explained in conjunction with the accompanying drawings, or will be learned through the practice of the present invention. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a three-dimensional structural diagram of a drift tube linear accelerator provided in an embodiment of the present invention.

[0017] Figure 2 This is a schematic diagram of the internal structure of a drift tube linear accelerator provided in an embodiment of the present invention.

[0018] Figure 3 This is a longitudinal symmetrical cross-sectional view of a drift tube linear accelerator provided in an embodiment of the present invention.

[0019] Figure 4 This is a three-dimensional structural diagram of the first drift tube provided in an embodiment of the present invention.

[0020] Figure 5 This is a three-dimensional structural diagram of the second drift tube provided in an embodiment of the present invention.

[0021] Figure label: 10. Cavity; 11. Beam aperture; 20. First crossbeam; 30. Second crossbeam; 40. Support rod; 50. Drift tube; 51. Opening slot; 50a. First drift tube; 50b. Second drift tube. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0023] In an embodiment of the present invention, a drift tube linear accelerator is described.

[0024] like Figures 1 to 3As shown, the drift tube linear accelerator mainly includes a cavity 10, a drift tube 50, a first crossbeam 20, a second crossbeam 30, and a support rod 40.

[0025] The cavity 10 is configured as a shell structure with an internal cavity. The cavity can be a cylindrical space or a cuboid space.

[0026] The drift tube 50 is configured as a square tube with open slots 51 at both ends. Several drift tubes 50 are arranged at intervals within the cavity. Furthermore, the central axis of each drift tube 50 coincides with the central axis of the cavity cylinder 10.

[0027] The first crossbeam 20 is installed at the upper part of the cavity. The second crossbeam 30 is installed at the lower part of the cavity.

[0028] Specifically, a plurality of drift tubes 50 are arranged at intervals along the central axis of the cavity 10 within the cavity. Both the first crossbeam 20 and the second crossbeam 30 are provided with a plurality of support rods 40. The support rods 40 on the first crossbeam 20 and the second crossbeam 30 are arranged alternately and connected to the drift tubes 50 in a one-to-one correspondence.

[0029] Compared to the complex connection between the traditional cylindrical drift tube 50 and the support rod 40, the drift tube 50 in this application adopts a square tube structure with more positioning planes, which is beneficial for connection and fixation with the support rod 40. A single drift tube 50 can be easily set inside the cavity 10 with only one support rod 40, which simplifies the structure, reduces the lateral dimension of the cavity 10, facilitates collimation measurement, and ensures more accurate results.

[0030] Furthermore, the first crossbeam 20 and the second crossbeam 30 are respectively connected to the positive electrode and the negative electrode. Specifically, the first crossbeam 20 is connected to the positive electrode, and the second crossbeam 30 is connected to the negative electrode, or vice versa, thereby creating a potential difference between two adjacent drift tubes 50 to establish a radio frequency electric field between the adjacent drift tubes 50.

[0031] Furthermore, both the first crossbeam 20 and the second crossbeam 30 extend from the left end of the cavity 10 to the right end of the cavity 10. Moreover, the first crossbeam 20 and the second crossbeam 30 are symmetrically arranged with respect to the central axis of the cavity 10.

[0032] For example, a first crossbeam 20 extends downward from the top of the cavity, and a second crossbeam 30 extends upward from the bottom of the cavity, with a gap between the first crossbeam 20 and the second crossbeam 30. A drift tube 50 is suspended between the first crossbeam 20 and the second crossbeam 30 by a support rod 40.

[0033] The cavity 10 has beam holes 11 at both ends for connecting the inside and outside of the cavity. The central axis of the beam holes 11 coincides with the central axis of the cavity 10.

[0034] Furthermore, any two adjacent drift tubes 50 are positioned opposite each other with the ends of the opening groove 51 extending in different directions.

[0035] A potential difference exists between the opposite ends of adjacent drift tubes 50, and the extension directions of the opening slots 51 are perpendicular to each other. The electric field formed by the potential difference has components along the beam direction and laterally (i.e., horizontally or vertically). The linear accelerator utilizes this potential difference to accelerate protons or heavy ions, and the perpendicular relationship of the opening slots 51 enables lateral focusing and defocusing of the beam. The lateral component of the potential difference is related to the extension direction of the opening slots 51.

[0036] Specifically, the drift tube 50 includes a first drift tube 50a for laterally focusing the beam.

[0037] like Figure 2 and Figure 4 As shown, one end of the first drift tube 50a has a notch on its horizontal sidewall, and the other end of the first drift tube 50a has a notch on its vertical sidewall, so that the two ends of the first drift tube 50a form opening grooves 51 with different extending directions.

[0038] The slots 51 at both ends of the first drift tube 50a extend horizontally and vertically, respectively, which can separate the electric focusing forces in the horizontal and vertical directions, allowing the beam to alternately focus and defocus in the horizontal and vertical directions, which is beneficial for lateral beam control. Because traditional linear accelerators use cylindrical drift tubes 50, they cannot distinguish between the electric focusing forces in the horizontal and vertical directions. Usually, they focus or defocus simultaneously in the horizontal and vertical directions, causing coupling effects in the lateral beam dynamics, which is not conducive to envelope control and beam transmission.

[0039] By employing the first drift tube 50a in this invention, the electrical focusing functions in the horizontal and vertical directions can be separated. That is, in a single acceleration unit, there is only a focusing force in one direction and a defocusing force in the other direction (horizontal focusing with vertical defocusing or horizontal defocusing with vertical focusing), similar to the effect of a quadrupole magnet. This weakens the coupling effect of the beam in the two directions, helps to control the lateral envelope of the beam, and improves beam quality and transmission efficiency.

[0040] Meanwhile, the drift tube 50 also includes a second drift tube 50b for focus / defocus conversion.

[0041] like Figure 2 and Figure 5As shown, the second drift tube 50b has notches at both ends of its horizontal sidewall or at both ends of its vertical sidewall, so that the two ends of the second drift tube 50b form openings 51 with the same extending direction.

[0042] In particular, the first drift tube 50a is arranged in the cavity 10 in two postures: one is that the end of the first drift tube extending vertically with the opening groove 51 faces the left end of the cavity 10, and the other is that the end of the first drift tube extending horizontally with the opening groove 51 faces the left end of the cavity 10.

[0043] Correspondingly, the second drift tube 50b is also arranged in two configurations within the cavity 10: one is that the second drift tube 50b extends vertically with an open groove 51, and the other is that the second drift tube 50b extends horizontally with an open groove 51. Thus, a total of four types of drift tubes 50 can be arranged within the cavity 10: two for horizontal and vertical focusing, and two for focusing / defocusing conversion.

[0044] Multiple first drift tubes 50a are arranged consecutively in the same orientation to superimpose focusing intensity in a set direction corresponding to the orientation. Each first drift tube 50a has a focusing intensity, and the consecutive arrangement can superimpose focusing intensity in a specific direction. At the same time, by adjusting the number of consecutive arrangement of first drift tubes 50a in the same orientation, the cumulative electric focusing intensity can be flexibly adjusted, expanding the range of parameter selection in beam dynamics design.

[0045] Based on the type and energy of the ion beam, the number of consecutively arranged first drift tubes 50a with the same orientation can be optimized to obtain a reasonable periodic focusing structure, thereby optimizing the lateral envelope of the beam and obtaining a high-quality, high-transmission-efficiency ion beam.

[0046] Furthermore, the second drift tube 50b is disposed between two first drift tubes 50a with different orientations to form a periodic FODO focusing structure.

[0047] By setting a second drift tube 50b between two first drift tubes 50a with different orientations to switch between convergence and divergence, a periodic FODO focusing structure similar to the strong focusing principle of an accelerator can be obtained, thereby realizing a specific beam dynamics design scheme.

[0048] Specifically, a periodic FODO focusing structure is an important repeating unit in particle accelerator design, which maintains stable particle beam propagation through a series of components arranged in a specific order. A basic FODO unit consists of a focusing magnet (F), a drift space (O), a defocusing magnet (D), and another drift space (O). In a periodic FODO structure, these basic units are repeatedly arranged along the beam path, forming a chain of FODO units.

[0049] In this embodiment, the drift tube 50 is set as a square tube and open slots 51 are set at both ends to form a semi-open square drift tube 50. By mixing and arranging the square drift tubes 50, the linear accelerator can maintain a high acceleration gradient in the longitudinal direction and have a strong focusing force in the transverse direction, thereby shortening the length of the linear accelerator and improving the quality of the extracted beam and the transmission efficiency of the linear accelerator.

[0050] Based on the above embodiments, another embodiment of the present invention introduces a drift tube type linear accelerator. Inside the cavity, the length of the drift tube 50 gradually increases from one end of the cavity 10 to the other end.

[0051] like Figure 3 As shown, several drift tubes 50 are arranged in the cavity in such a way that their length gradually increases from one end of the cavity 10 to the other end of the cavity 10.

[0052] Compared to the traditional cylindrical drift tube 50, if the through-hole for beam passage in the drift tube 50 of this application has the same size as the through-hole for beam passage in the cylindrical drift tube 50, then the transverse cross-section of the drift tube 50 of this application will be significantly larger than that of the cylindrical drift tube 50. This results in the drift tube linear accelerator with a square tube structure having a greater transverse beam acceptance, which is beneficial to improving the output current intensity of the entire accelerator system.

[0053] In summary, the drift tube linear accelerator of this application sets the drift tube 50 as a square tube structure and arranges them in a mixed manner to form a novel acceleration structure. This acceleration structure enables drift tube linear accelerators involving protons and heavy ions to have both a high acceleration gradient and stronger lateral focusing force. It allows for free adjustment of the focusing and defocusing effects and their intensity, which is beneficial for beam envelope control and dynamics design, thereby improving the extracted beam quality and transmission efficiency of the linear accelerator. Simultaneously, this structure offers greater beam acceptance, a simpler collimation installation method, and lower manufacturing, processing, and operation and maintenance costs.

[0054] Meanwhile, the drift tube linear accelerator in this application will have a profound impact on fields such as proton and heavy ion-based tumor cancer treatment, materials irradiation, radioactive isotope production, and aerospace research, bringing huge economic benefits.

[0055] In the description of the embodiments of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0056] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0057] In embodiments of the present invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0058] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms are not limited to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A drift tube type linear accelerator, characterized in that, include: The cavity tube (10) is configured as a shell structure with an internal cavity; The drift tube (50) is configured as a square tube with open grooves (51) at both ends; The first crossbeam (20) is installed on the upper part of the cavity; The second crossbeam (30) is installed at the lower part of the cavity; Among them, a plurality of drift tubes (50) are arranged at intervals along the central axis of the cavity (10) in the cavity, and the first crossbeam (20) and the second crossbeam (30) are both provided with support rods (40). The support rods (40) on the first crossbeam (20) and the second crossbeam (30) are arranged alternately and connected to the drift tubes (50) one by one. The first crossbeam (20) is connected to the positive electrode, and the second crossbeam (30) is connected to the negative electrode, for establishing a radio frequency electric field between adjacent drift tubes (50); The drift tube (50) includes a first drift tube (50a) for laterally focusing the beam. One end of the first drift tube (50a) has a notch on its horizontal sidewall, and the other end of the first drift tube (50a) has a notch on its vertical sidewall, so that the two ends of the first drift tube (50a) form opening grooves (51) with different extending directions. The drift tube (50) further includes a second drift tube (50b) for focusing and defocusing conversion. The second drift tube (50b) has notches at both ends of its horizontal sidewall or at both ends of its vertical sidewall, so that the two ends of the second drift tube (50b) form openings (51) with the same extending direction.

2. The drift tube linear accelerator according to claim 1, characterized in that, The length of the drift tube (50) gradually increases from one end of the cavity (10) to the other end of the cavity (10).

3. The drift tube linear accelerator according to claim 2, characterized in that, Any two adjacent drift tubes (50) are opposite ends with different extension directions of the opening groove (51).

4. The drift tube linear accelerator according to claim 3, characterized in that, The first drift tube (50a) is arranged in the cavity (10) in two postures: one is that the first drift tube (50a) extends vertically with an opening groove (51) facing the left end of the cavity (10), and the other is that the first drift tube (50a) extends horizontally with an opening groove (51) facing the left end of the cavity (10).

5. The drift tube linear accelerator according to claim 4, characterized in that, Multiple first drift tubes (50a) are arranged in a continuous manner with the same orientation to superimpose focusing intensity in a set direction corresponding to the orientation.

6. The drift tube linear accelerator according to claim 5, characterized in that, The second drift tube (50b) is positioned between two first drift tubes (50a) with different orientations to form a periodic FODO focusing structure.

7. The drift tube linear accelerator according to claim 6, characterized in that, The first crossbeam (20) and the second crossbeam (30) both extend from the left end of the cavity (10) to the right end of the cavity (10) and are symmetrically distributed relative to the central axis of the cavity (10).

8. The drift tube linear accelerator according to claim 7, characterized in that, The cavity (10) is provided with beam holes (11) at both ends for connecting the inside and outside of the cavity, and the central axis of the beam hole (11) coincides with the central axis of the cavity (10).

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