Accelerating device

Abstract

The invention relates to an acceleration device. The acceleration device comprises a drift tube linear accelerator and a radio frequency quadrupole field accelerator. And the radio frequency quadrupole field accelerator is directly connected with the drift tube linear accelerator. The radio frequency quadrupole field accelerator includes an electrode. In the proton transmission direction, the electrode is of an integrated structure and comprises a conventional part and an extension part. The extension part comprises one or more bunching units, the bunching units have negative synchronous phases, and the bunching capability of the radio frequency quadrupole field accelerator is adjusted by setting the length, the number and the synchronous phases of the bunching units; the aperture and the modulation coefficient of the bunching unit are the same as those of the previous unit, and the previous unit is a conventional part or the bunching unit.

Description

[0001] This application is a divisional application. The application number of the original application is 202411454775.6, the application date is October 17, 2024, and the name of the invention is "Radio Frequency Quadrupole Field Accelerator and Acceleration Device". Technical Field

[0002] The present application relates to the field of particle accelerators, and in particular to an acceleration device. Background Art

[0003] Boron Neutron Capture Therapy (BNCT) is a cell-level targeted tumor radiotherapy. Traditional BNCT mainly relies on nuclear reactors as neutron sources, but it is difficult to popularize in medical institutions due to its high construction and maintenance costs. With the development of accelerator technology, accelerator-based boron neutron capture therapy (AB-BNCT) driven by accelerators has the advantages of high current intensity, high duty cycle, high transmission efficiency, etc., making AB-BNCT safer, more economical and easy to promote.

[0004] Some accelerators are equipped with radio frequency quadrupole (RFQ) accelerators. The working principle of the RF quadrupole accelerator is based on the radio frequency electric field. The RF quadrupole accelerator uses four electrodes, and a radio frequency electric field is applied to the electrodes. When a charged particle passes through the space between these electrodes, the radio frequency electric field exerts a force on the particle. The change in the radio frequency electric field of the RF quadrupole accelerator causes the force to change alternately in different directions, thereby accelerating the particle while moving forward. In addition, the force exerted on the particle by the radio frequency electric field of the RF quadrupole accelerator enables the particle to maintain a certain degree of focus.

[0005] After the particles leave the RF quadrupole accelerator, they lose the focusing effect of the RF electric field on the particles and will diverge, reducing the acceleration performance of the accelerator. Some current accelerators add a bunching cavity structure after the RF quadrupole accelerator to maintain the focusing degree of the particles, but the increase of the bunching cavity will increase the size of the accelerator. Summary of the invention

[0006] The present application provides an acceleration device to solve some or all of the deficiencies in the related art.

[0007] The acceleration device of the present application includes a drift tube linear accelerator and a radio frequency quadrupole accelerator; the radio frequency quadrupole accelerator is directly connected to the drift tube linear accelerator; the radio frequency quadrupole accelerator includes electrodes; wherein,

[0008] Along the proton transport direction, the electrode is an integrated structure, including a regular portion and an extended portion;

[0009] The extension part includes one or more bunching units, each of which has a negative synchronization phase, and the bunching capability of the radio frequency quadrupole accelerator is adjusted by setting the length, number and synchronization phase of the bunching units;

[0010] The aperture and modulation factor of the beamforming unit are the same as those of the previous unit, which is a conventional unit or a beamforming unit.

[0011] Furthermore, the length of the i-th bunching unit is:

[0012]

[0013] in:

[0014] β is the relative velocity of the particles at the inlet of the bunching unit;

[0015] λ is the wavelength of the incident light;

[0016] φ i is the synchronization phase of the i-th beamforming unit;

[0017] φ s is the synchronization phase of the previous unit of the i-th bunching unit;

[0018] L pc is the length of the unit before the i-th bunching unit.

[0019] Further, the synchronization phase of the conventional part is -30°, the extended part includes a first bunching unit and a second bunching unit, and the synchronization phases of the first bunching unit and the second bunching unit along the proton transmission direction are respectively -60° and -90°.

[0020] Further, the length of the first beam-forming unit is greater than or equal to 35 mm and less than or equal to 40 mm;

[0021] The length of the second bunching unit is greater than or equal to 55 mm and less than or equal to 60 mm.

[0022] Furthermore, the drift tube linear accelerator comprises:

[0023] A first coupling part, a second coupling part and a coupling member; the coupling member is disposed between the first coupling part and the second coupling part, and couples the first coupling part and the second coupling part to enclose and form an accelerating cavity of the drift tube linear accelerator;

[0024] Wherein, the coupling component includes a coupling shell, a magnet drift tube and a drift tube support rod; the coupling shell surrounds a coupling cavity of the coupling component; the magnet drift tube is arranged in the coupling cavity; the drift tube support rod is arranged in the coupling cavity and connects the magnet drift tube and the coupling shell; the magnet drift tube is coaxially arranged with the first coupling part and the second coupling part to form a beam channel of the drift tube linear accelerator in the acceleration cavity.

[0025] Furthermore, the coupling component also includes a quadrupole magnet; the quadrupole magnet is arranged in the magnet drift tube.

[0026] Furthermore, the coupling member includes a water cooling pipe; the water cooling pipe is distributed around the circumference of the magnet drift tube and extends along the drift tube support rod to the surface of the coupling housing.

[0027] Further, a plurality of drift tubes are arranged in the first coupling part and the second coupling part, and the plurality of drift tubes are arranged at intervals to form an acceleration gap of the drift tube linear accelerator in the acceleration cavity;

[0028] Wherein, six drift tubes are arranged in the first coupling part;

[0029] And / or, five drift tubes are arranged in the second coupling part.

[0030] Furthermore, the drift tube linear accelerator further comprises a focusing slot;

[0031] The focusing groove is arranged at an end of the first coupling part away from the coupling member; the focusing groove is recessed toward the interior of the accelerating cavity; and / or, the focusing groove is arranged at an end of the second coupling part away from the coupling member; the focusing groove is recessed toward the interior of the accelerating cavity.

[0032] The technical solution provided by the embodiments of the present application may have the following beneficial effects:

[0033] It can be seen from the above embodiments that the accelerator of the present application does not need to set a bunching cavity after the exit end of the radio frequency quadrupole accelerator to achieve beam bunching. The beam leaving the exit end maintains a small beam divergence and a high beam energy under the action of the extension part to enter the drift tube linear accelerator for the next particle process. This reduces the matching length required for the beam leaving the radio frequency quadrupole accelerator. The reduction in matching length is conducive to reducing the overall size of the accelerator in the longitudinal direction. At the same time, the extension part can also ensure the bunching ability of the beam, thereby ensuring the beam quality of the accelerator.

[0034] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 Shown is a simplified schematic diagram of one embodiment of the acceleration device of the present application.

[0037] Figure 2 Shown is a simplified schematic diagram of a partial cross section of an embodiment of a radio frequency quadrupole field accelerator of the present application.

[0038] Figure 3 This is the electrode envelope diagram of the radio frequency quadrupole accelerator.

[0039] Figure 4 Shown is a simplified microscopic schematic diagram of an embodiment of an electrode of a radio frequency quadrupole field accelerator of the present application.

[0040] Figure 5 Shown is a diagram of the electric field intensity distribution at different positions in the longitudinal direction of a radio frequency quadrupole accelerator provided with different numbers of beam-focusing units.

[0041] Figure 6 The particle distribution diagram at the exit of the RF quadrupole accelerator with different numbers of bunching units is shown. The area inside the elliptical line around the particle distribution contains 99.9% of the accelerated particles.

[0042] Figure 7 A cross-sectional schematic diagram of an embodiment of a drift tube linear accelerator of the accelerating device of the present application is shown.

[0043] Figure 8 It is a cross-sectional schematic diagram of an embodiment of a magnet drift tube of the drift tube linear accelerator of the present application.

[0044] Description of reference numerals:

[0045] 100 acceleration device, 1 radio frequency quadrupole field accelerator, 11 entrance end, 12 exit end, 13 wall, 14 cavity, 15 electrode, 151 conventional part, 1511 conventional unit, 152 extension part, 1521 bunching unit, 2 ion source, 3 drift tube linear accelerator, 31 first coupling part, 311 first opening, 312 feeding hole, 32 second coupling part, 321 second opening, 322 feeding hole, 33 coupling part, 331 coupling shell, 332 magnet drift tube, 333 drift tube support rod, 334 circulation hole, 335 water cooling pipe, 336 quadrupole magnet, 34 acceleration cavity, 35 drift tube, 36 acceleration gap, 37 bunching slot, X transverse direction, Y vertical direction, Z longitudinal direction. DETAILED DESCRIPTION

[0046] Here, the technical solutions in the embodiments (or "implementations") of the present application will be described clearly and completely in conjunction with the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements.

[0047] If there are terms involving directional indications or positional relationships in the embodiments of the present application (such as up, down, left, right, front, back, inside, outside, top, bottom, center, vertical, horizontal, longitudinal, transverse, length, width, counterclockwise, clockwise, axial, radial, circumferential, etc.), such terms are only used to explain the relative positional relationship, movement, etc. between the components under a certain specific posture (as shown in the accompanying drawings); if the specific posture changes, the directional indication or positional relationship will also change accordingly. In addition, the terms "first", "second", etc. involved in the embodiments of the present application are only used for the purpose of convenience of description and cannot be understood as indicating or implying relative importance.

[0048] refer to Figure 1 and Figure 2 The present application provides an accelerator 100. The accelerator 100 includes an ion source 2, a radio frequency quadrupole field accelerator 1, and a drift tube linear accelerator (DTL accelerator) 3. The radio frequency quadrupole field accelerator 1 includes an inlet end 11 and an outlet end 12. The inlet end 11 of the radio frequency quadrupole field accelerator 1 is connected to the ion source 2, and the outlet end 12 is directly connected to the drift tube linear accelerator.

[0049] The radio frequency quadrupole accelerator 1 includes four electrodes. A radio frequency electric field is applied to the electrodes. When the charged particles emitted by the ion source 2 pass through the space between the four electrodes, the radio frequency electric field exerts a force on the particles, and this force changes alternately in different directions, causing the particles to be accelerated while moving forward.

[0050] like Figure 2As shown, the particle beam is distributed in the RF quadrupole accelerator 1 along the transverse direction X, the vertical direction Y and the longitudinal direction Z. Hereinafter, the beam in the plane where the transverse direction X and the vertical direction Y are located is referred to as the transverse beam, and the beam in the plane where the longitudinal direction Z is located is referred to as the longitudinal beam. In the traditional design, the beam matching of the transverse beam and the longitudinal beam between the RF quadrupole accelerator 1 and the drift tube linear accelerator 3 is achieved using a bunching cavity. Beam matching refers to keeping the beam parameters of the particle beam leaving the RF quadrupole accelerator 1 stable so as to enter the drift tube linear accelerator 3 for the next particle process. The beam parameters include parameters such as beam divergence and beam energy. However, setting a bunching cavity between the RF quadrupole accelerator 1 and the drift tube linear accelerator 3 will increase the size of the acceleration device 100 in the longitudinal direction Z and make the structure more complicated.

[0051] To this end, the present application makes improvements to the radio frequency quadrupole field accelerator 1. The radio frequency quadrupole field accelerator 1 of the present application includes a wall 13 and an electrode 15. The wall 13 surrounds a cavity 14 forming the radio frequency quadrupole field accelerator 1. The cavity 14 extends along the longitudinal direction Z. The electrode 15 is arranged in the cavity 14 and connected to the wall 13. Along the proton transmission direction, that is, the longitudinal direction Z, the electrode 15 is an integrated structure, including a conventional part 151 and an extension part 152. The extension part includes one or more beamforming units 1521. The beamforming unit 1521 has a negative synchronization phase. By setting the length, number and synchronization phase of the beamforming unit 1521, the beamforming ability of the radio frequency quadrupole field accelerator 1 can be adjusted. The aperture and modulation coefficient of the beamforming unit 1521 are the same as the aperture and modulation coefficient of the previous unit. The previous unit is the conventional part 151 or the beamforming unit 1521.

[0052] The electrode 15 referred to in this embodiment should be understood as Figure 2 The sum of the four electrodes shown, rather than a single electrode. The particles in the beam are accelerated to acquire energy under the influence of the electric field of the conventional part 151. In the radio frequency quadrupole accelerator 1, the phase refers to the time position of the position of the particle in the radio frequency electric field relative to the change of the electric field. The synchronization phase refers to the phase position in the radio frequency electric field where the particle can absorb energy most effectively. Under different synchronization phases, the acceleration effect and focusing effect of the particles in the radio frequency quadrupole accelerator 1 are different.

[0053] The electrode 15 of the radio frequency quadrupole field accelerator 1 of the present application is extended with an extension portion 152 after the conventional portion 151. The beam passes through the position of the extension portion 152 after being accelerated by the conventional portion 151. The extension portion 152 can adjust the bunching ability of the radio frequency quadrupole field accelerator 1 by setting the length, number and synchronous phase of the bunching unit 1521, thereby realizing the bunching of particles. This improves the bunching ability of the radio frequency quadrupole field accelerator 1. In addition, the extension portion 152 is arranged close to the outlet end 12 along the longitudinal direction Z, so that the beam leaving the outlet end 12 maintains a small beam divergence and a high beam energy under the action of the extension portion 152 to enter the next particle process.

[0054] The modulation coefficient is an important design parameter of the RF four-stage field accelerator 1. It describes the ratio of the maximum deviation of the electrode surface to the average radius of the electrode 15, and can characterize the electrode envelope to a certain extent, that is, the outer contour or shape of the electrode 15 structure. The aperture and modulation coefficient of the beam unit 1521 are consistent with the previous unit, which can ensure the smoothness of the envelope between adjacent units, thereby ensuring the spatial distribution of the RF electric field, the focusing effect of the beam and the acceleration efficiency.

[0055] refer to Figure 3 . Figure 3 Electrode envelope diagram after the extension part 152 is set for the radio frequency quadrupole field accelerator 1. Among them, the extension part 152 of this embodiment includes two bunching units 1521. Along the transmission direction of protons (i.e., the longitudinal direction Z), they are respectively called the first bunching unit and the second bunching unit. The electrode modulation unit is a key part for generating the required radio frequency electric field distribution in the radio frequency quadrupole field accelerator. The modulation unit can generate a quadrupole field in the transverse direction X and the vertical direction Y, and provide an accelerating electric field in the longitudinal direction Z. This application does not limit the specific setting of the modulation unit.

[0056] Figure 3 The horizontal axis is the length position of the electrode 15 in the longitudinal direction Z, and the vertical axis is the size of the electrode envelope. The black line is the envelope of the electrode 15 in the longitudinal direction Z, and the red line is the envelope of the electrode 15 in the transverse direction X and the vertical direction Y. Figure 3 It can be seen that the electrode 15 of the present application has a smooth envelope at the transition position between the conventional portion 151 and the extended portion 152, which is beneficial to ensuring the focusing effect of the beam and meeting the acceleration requirements.

[0057] The extension portion 152 should be understood as a portion added to the electrode 15 on the basis of the same outlet energy of the radio frequency quadrupole field accelerator 1, and the length of the electrode 15 of the radio frequency quadrupole field accelerator 1 with different outlet energies should not be compared. For example, the dimension of the extension portion 152 in the longitudinal direction Z is referred to as A. In an embodiment where the outlet energy of the radio frequency quadrupole field accelerator 1 is 1.1 MeV, if the electrode length of the existing radio frequency quadrupole field accelerator is B, then the electrode length of the radio frequency quadrupole field accelerator 1 of the present application is B+A.

[0058] Based on the foregoing description, the accelerator 100 provided with the radio frequency quadrupole accelerator 1 of the present application does not need to set a bunching cavity after the outlet end 12 of the radio frequency quadrupole accelerator 1 to achieve beam bunching. The beam leaving the outlet end 12 maintains a small beam divergence and a high beam energy under the action of the extension 152 to enter the drift tube linear accelerator 3 for the next particle process. This reduces the matching length required for the beam leaving the radio frequency quadrupole accelerator 1. The reduction in the matching length is conducive to reducing the overall size of the accelerator 100 in the longitudinal direction Z, and the extension 152 can also ensure the beam bunching ability, thereby ensuring the beam quality of the accelerator 100.

[0059] It should be noted that the direct connection between the radio frequency quadrupole field accelerator 1 and the drift tube linear accelerator 3 referred to in this application should be understood as the beam directly entering the drift tube linear accelerator 3 after leaving the radio frequency quadrupole field accelerator 1, without passing through other structures such as a focusing cavity. In other words, the direct connection between the radio frequency quadrupole field accelerator 1 and the drift tube linear accelerator 3 should not be understood as a physical direct connection relationship.

[0060] Figure 4 It is a microscopic exploded view of the side of the electrode 15. It should be noted that, Figure 4 The size of the conventional unit 1511 in the figure is different from that of the beamforming unit 1521, which is only for the convenience of illustration and description. In practice, since the aperture and modulation coefficient of the beamforming unit 1521 are the same as those of the previous unit, the sizes of the beamforming unit 1521 and the forward conventional unit 1511 should be the same.

[0061] The electrode 15 can be divided into a plurality of microscopic units in the longitudinal direction Z. The conventional portion 151 includes a plurality of connected conventional units 1511. The extension portion 152 includes a focusing unit 1521. The focusing capability of the extension portion 152 is determined to some extent by the synchronization phase of the focusing unit 1521.

[0062] Energy gain of the particle in the longitudinal direction Z ΔW s The calculation formula is:

[0063]

[0064] Among them, q is the charge, e is the charge of the charged particle, E0 is the average electric field strength, T is the transit time factor T=π / 4, L is the moving distance of the particle in the longitudinal direction Z, is the phase of the particle.

[0065] In order to achieve particle acceleration, the energy increment of the particle must be non-negative, so the cosine value of the particle phase should be greater than or equal to zero. It can be seen that the phase of the particle should be greater than or equal to -90 degrees and less than or equal to 90 degrees.

[0066] According to the oscillation angular frequency formula of the particle doing phase oscillation motion:

[0067]

[0068] Where c is the speed of light, λ is the wavelength of the incident light, e is the charge of the charged particle, E0 is the average electric field strength, T is the transit time factor T = π / 4, ε0 is the vacuum dielectric constant, β s is the ideal particle relative velocity, γ s is the relativistic factor, is the particle phase.

[0069] In order for the oscillation angular frequency formula to hold true, it is known that the sine value of the particle phase should be a non-positive number. It is known that the phase of the particle should be less than or equal to 0 degrees. Combined with the energy gain formula, it can be seen that the phase of the particle should be between -90 degrees and 0 degrees to keep the particle in stable motion. The closer the phase is to 0 degrees, the higher the energy gain, which means the better the acceleration effect of the particle. Since the particle is accelerated along the longitudinal direction Z, it means that the component of the force exerted by the RF electric field on the particle at this time is mainly along the Z direction, and the component in the transverse direction X or the vertical direction Y is small. It can be seen that the bunching effect of this phase on the particle is slightly weak. On the contrary, the closer the phase is to -90 degrees, the lower the energy gain, and the acceleration effect of the ions is weaker at this time. Then the component of the force exerted by the RF electric field on the particle in the transverse direction X or the vertical direction Y increases, and the bunching effect is good.

[0070] In some embodiments, only one beamforming unit 1521 may be provided. For better beamforming effect, the synchronization phase of the beamforming unit 1521 may be set to -90 degrees, thereby maximizing the beamforming effect of the beamforming unit 1521 .

[0071] In some other embodiments, a plurality of beam-forming units 1521 may be provided. The plurality of beam-forming units 1521 are connected, and the synchronization phases of at least some of the beam-forming units 1521 are different. In fact, the performance of the radio frequency quadrupole accelerator 1 is actually also affected by the number of beam-forming units 1521. Specifically, Figure 5The electric field intensity distribution diagram of the radio frequency quadrupole field accelerator 1 provided with different numbers of bunching units 1521 at different positions in the longitudinal direction Z. The black curve, red curve, blue curve and purple curve correspond to the embodiments of the radio frequency quadrupole field accelerator 1 without bunching unit 1521, the radio frequency quadrupole field accelerator 1 with one bunching unit 1521, the radio frequency quadrupole field accelerator 1 with two bunching units 1521 and the radio frequency quadrupole field accelerator 1 with three bunching units 1521, respectively. For the sake of simplicity, Figure 5 The partial embodiment shown only intercepts the electric field strength curve from the location where the beam-forming unit 1521 is provided to the exit end 12, and the waveforms of the remaining locations of the radio frequency quadrupole accelerator 1 are basically consistent with the waveforms of the locations shown. The end point of the curve is the location of the exit end 12 of the radio frequency quadrupole accelerator 1.

[0072] As can be seen from the accompanying drawings, as the number of bunching units 1521 increases, the horizontal coordinate of the outlet end 12 increases, which means that the size of the radio frequency quadrupole field accelerator 1 in the longitudinal direction Z increases. When there is only one bunching unit 1521, the electric field strength increases the most compared to the embodiment in which the bunching unit 1521 is not provided. The increase in the electric field strength will cause sparks inside the cavity 14 of the radio frequency quadrupole field accelerator 1. Sparks cause the power of the acceleration device 100 to be unstable, thereby affecting the stability of particle acceleration. At the same time, the increase in the electric field strength will also increase the risk of dielectric breakdown, resulting in electric field failure.

[0073] When three bunching units 1521 are provided, the increase in the electric field strength is less than that of the embodiment with one bunching unit 1521, but still greater than that of the embodiment with two bunching units 1521, and the size of the radio frequency quadrupole accelerator 1 in the longitudinal direction Z is the largest. The effect of the electrode 15 provided with two bunching units 1521 on the electric field strength is close to the effect of the electrode 15 without a bunching unit 1521 on the electric field strength, which shows that the two bunching units 1521 have little effect on the increase in the electric field strength, and can also effectively control the size of the radio frequency quadrupole accelerator 1 in the longitudinal direction Z.

[0074] As mentioned above, when the phase of the bunching unit 1521 is close to -90 degrees, the bunching ability is good. However, the inventors have found through many simulation tests that if the phases of the two bunching units 1521 are set to -90 degrees, although the bunching ability is guaranteed to a certain extent, it will lead to a significant increase in the electric field strength to a certain extent. Therefore, in some embodiments, the extension 152 includes a first bunching unit and a second bunching unit. In the transmission direction of the protons (i.e., longitudinal direction Z), the synchronization phases of the first bunching unit and the second bunching unit are -60° and -90°, respectively. After many tests and adjustments, the inventors found that the phase setting method of this embodiment not only ensures the bunching ability of the extension 152, but also minimizes the influence of the extension 152 on the electric field strength.

[0075] Table 1 shows the output parameters of the embodiment of the radio frequency quadrupole accelerator 1 with an outlet energy of 1.1 MeV and including different numbers of beam-forming units 1521, wherein the synchronization phase of the conventional part is -30°:

[0076] Table 1

[0077]

[0078]

[0079] It should be noted that the phase arrangement of the plurality of beam-forming units 1521 in Table 1 is the phase of the beam-forming units 1521 sequentially arranged along the propagation direction of the protons.

[0080] As can be seen from the above table, when the number of bunching units 1521 is 2 and they are set at phases of -60 degrees and -90 degrees, the surface peak field is close to that of the embodiment in which no bunching unit 1521 is set, and is smaller than that of the embodiment in which one bunching unit 1521 is set. Similar to the increase in electric field intensity, the increase in surface peak field will lead to the risk of ignition and dielectric breakdown inside the accelerator 100. Compared with the embodiment in which one bunching unit 1521 is set, the value of the longitudinal phase distribution of the embodiment with two bunching units 1521 is significantly improved. The value of the longitudinal phase distribution is used to characterize the particle divergence and beam quality in the longitudinal direction Z. The higher the value of the longitudinal phase distribution, the lower the divergence of the ions and the better the quality of the beam.

[0081] Figure 6 The figure is a particle distribution diagram at the outlet end 12 of the radio frequency quadrupole field accelerator 1 provided with different numbers of bunching units 1521, wherein the setting parameters correspond to Table 1. The first row, the second row and the third row are the particle distribution diagrams of the radio frequency quadrupole field accelerator 1 with no bunching unit 1521, two bunching units 1521 and three bunching units 1521, respectively; the first column, the second column and the third column are the particle distribution diagrams of the cross section perpendicular to the transverse direction X, the cross section perpendicular to the vertical direction Y and the cross section perpendicular to the longitudinal direction Z, respectively. The red elliptical line in the figure is the area containing 99.9% of the accelerated particles. Particles of different colors in the distribution diagram refer to accelerated particles of different energies. The energy of the blue accelerated particles is smaller than the energy of the red accelerated particles.

[0082] The third column of pictures is a cross-sectional picture perpendicular to the longitudinal direction Z, so the bunching effect of the particles can be seen from the distribution diagram of the particles. The horizontal coordinate of the third column of pictures is the angle of the particle, and the vertical coordinate is the energy of the particle. The particle energy distribution position similarity of the radio frequency quadrupole field accelerator 1 without a bunching unit 1521 is high, and the angular distribution of the particles is discrete. At this time, the beam can be understood as a parallel beam. With the increase in the number of bunching units 1521, the distribution of particle energy diffuses, the angular distribution tightens, and the direction of the beam changes toward the longitudinal focused beam. It can be seen that the increase in the number of bunching units 1521 improves the compactness of the particles of the radio frequency quadrupole field accelerator 1 in the longitudinal direction Z, and improves the bunching effect of the radio frequency quadrupole field accelerator 1.

[0083] It can be seen from Table 1 that the embodiment with two bunching units 1521 has a smaller length of the electrode 15 in the longitudinal direction Z than the embodiment with three bunching units 1521, and the beam energy of the radio frequency quadrupole field accelerator 1 is higher. However, in fact, the longitudinal phase distribution of the radio frequency quadrupole field accelerator 1 provided with the bunching unit 1521 has been significantly improved, and the increase of the longitudinal emittance is slight, which verifies the effect of the extension part 152 of the present application.

[0084] In addition, the electrode 15 refers to Figure 2 The four electrodes shown in the figure, and the synchronous phases of the adjacent electrodes of the radio frequency quadrupole field accelerator 1 differ by 180 degrees. The phase of the extension portion 152 referred to in the present application should be understood as the synchronous phase of the four electrodes at the extension portion 152. For example, in an embodiment in which the synchronous phase of the extension portion 152 is -60 degrees, the synchronous phases of the four electrodes at the extension portion 152 are all -60 degrees, but the conventional portion 151 is still 180 degrees different in phase between adjacent electrodes. It should be understood that the synchronous phases of the four electrodes at the extension portion 152 may still have slight phase differences in actual production. This application will not go into details.

[0085] In the inventor's simulation experiment, the inventor found that the synchronization phase of the beam focusing unit 1521 is also affected by the size (i.e., length) of the beam focusing unit 1521 in the longitudinal direction Z. In the embodiment where the extension 152 includes only one beam focusing unit 1521, the size of the extension 152 in the longitudinal direction Z is the same as the size of the beam focusing unit 1521 in the longitudinal direction. In this embodiment, when the length of the beam focusing unit 1521 in the longitudinal direction Z is greater than or equal to 15 mm and less than or equal to 20 mm, the beam presents a good beam focusing effect in the longitudinal direction Z. The size of the beam focusing unit 1521 in the longitudinal direction can be 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, or any value therebetween.

[0086] In the embodiment where the extension 152 includes two beam-forming units 1521, the length of the first beam-forming unit in the longitudinal direction Z is greater than or equal to 35 mm and less than or equal to 40 mm; the length of the second beam-forming unit in the longitudinal direction Z is greater than or equal to 55 mm and less than or equal to 60 mm. When the dimensions of the two beam-forming units 1521 in the longitudinal direction Z are within the above range, the extension 152 has a small effect on the increase in the electric field intensity, and can effectively avoid power instability of the acceleration device 100, while having a good beam-forming effect.

[0087] The length of the bunching unit 1521 near the inlet end 11 in the longitudinal direction Z can be 35 mm, 36 mm, 37 mm, 38 mm, 39 mm, 40 mm or any value therebetween. The length of the bunching unit 1521 near the outlet end 12 in the longitudinal direction Z can be 55 mm, 56 mm, 57 mm, 58 mm, 59 mm, 60 mm or any value therebetween.

[0088] The number of the bunching units 1521 may be one or more. Through multiple derivations and verifications, the inventors found that the length of the i-th bunching unit 1521 in the longitudinal direction Z can be obtained by the following formula:

[0089]

[0090] in:

[0091] β is the relative velocity of particles on the side of the bunching unit 1521 close to the inlet end 11;

[0092] λ is the wavelength of the incident light; where βλ / 2 represents the period length;

[0093] φ i is the synchronization phase of the i-th beamforming unit 1521;

[0094] φ s is the synchronization phase of the previous unit of the i-th beamforming unit 1521;

[0095] L pc is the length of the previous unit of the i-th beam-forming unit 1521 in the longitudinal direction Z.

[0096] In the embodiment where there is only one beamforming unit 1521, φ s L is the synchronization phase of the adjacent normal unit 1511 on the side of the beamforming unit 1521 close to the inlet end 11. pc It is the length of the conventional unit 1511 in the longitudinal direction Z.

[0097] In the embodiment where there are two bunching units 1521, the bunching unit 1521 near the inlet end 11 is called the first bunching unit 1521, and the bunching unit 1521 near the outlet end 12 is called the second bunching unit 1521. When calculating the length of the first bunching unit 1521 in the longitudinal direction Z, φ s L is the synchronization phase of the adjacent conventional unit 1511 on the side of the first beamforming unit 1521 close to the inlet end 11. pc is the length of the conventional unit 1511 in the longitudinal direction Z. When calculating the length of the second beamforming unit 1521 in the longitudinal direction Z, φ s is the synchronization phase of the first beamforming unit 1521. pc It is the length of the first beam-forming unit 1521 in the longitudinal direction Z.

[0098] It can be known from the above formula that the phase of the beam-forming unit 1521 is associated with its size in the longitudinal direction Z, so the phase of the beam-forming unit 1521 can be designed and adjusted according to its size in the longitudinal direction Z, so that the adjustment of the phase is more intuitive. When a person skilled in the art designs the radio frequency quadrupole accelerator 1, the size of the beam-forming unit 1521 in the longitudinal direction Z can be set by first setting the desired phase value of the beam-forming unit 1521. Alternatively, a person skilled in the art can also calculate whether the phase of the beam-forming unit 1521 meets the requirements by setting the preset size of the beam-forming unit 1521 in the longitudinal direction Z, and adjust it according to the requirements.

[0099] Table 2 summarizes the main dynamic parameters of the radio frequency quadrupole field accelerator 1 with the extension 152. The radio frequency quadrupole field accelerator 1 accelerates a 25 mA continuous wave proton beam to 1.1 ± 10% MeV, with a frequency of 165 Hz, an inter-electrode voltage of 65 kV, a transmission efficiency of 99.6%, a cycle length of 46.0 mm, and a length of the electrode 15 of 2.54 m ± 1%. For the radio frequency quadrupole field accelerator 1 with an outlet energy of 1.1 MeV, the cycle length (βλ / 2) corresponds to 46.0 mm.

[0100] Table 2

[0101] parameter value Frequency / MHz 165 Entry energy / keV 40 Export energy / MeV 1.17 Interelectrode voltage kV 65 Current intensity mA 25 Electrode length / mm 2506.83 Number of conventional units 166 Maximum modulation factor 2.14 Number of bunching units 2 Synchronous phase / deg -90～-25 Transverse direction outlet normalized rms emittance / mm·mrad 0.231 Normalized rms emittance at vertical outlet / mm·mrad 0.239 Normalized rms emittance at the longitudinal exit deg·MeV 0.07 Peak field strength MV·m-1 15.73 Kp coefficient 1.15 Transverse and vertical emissivity increase / % ＜15 Transmission efficiency % 99.6

[0102] The exit normalized rms emittance is a parameter that describes the phase space distribution characteristics of the particle beam when it leaves the accelerator. It eliminates the influence of beam size through normalization processing and is an important indicator for measuring beam quality. Low exit normalized rms emittance means that the particle beam has a good focusing state and a small divergence. As can be seen from Table 2, the radio frequency quadrupole field accelerator 1 of the present application has a very low exit normalized rms emittance in the longitudinal direction Z by providing an extension 152, which means that the beam of the radio frequency quadrupole field accelerator 1 is in a good focusing state after being bunched by the extension 152.

[0103] The drift tube linear accelerator 3 mentioned above may be any common drift tube accelerator 3 .

[0104] refer to Figure 7 In some embodiments, the drift tube linear accelerator 3 includes: a first coupling portion 31, a second coupling portion 32, and a coupling member 33. The coupling member 33 is disposed between the first coupling portion 31 and the second coupling portion 32, and couples the first coupling portion 31 and the second coupling portion 32 to enclose an accelerating cavity 34 of the drift tube linear accelerator 3. The coupling member 33 includes a coupling housing 331, a magnet drift tube 332, and a drift tube support rod 333. The coupling housing 331 encloses a coupling cavity of the coupling member 33. The magnet drift tube 332 is disposed in the coupling cavity. The drift tube support rod 333 is disposed in the coupling cavity and connects the magnet drift tube 332 and the coupling housing 331. The magnet drift tube 332 is coaxially disposed with the first coupling portion 31 and the second coupling portion 32 to form a beam channel of the drift tube linear accelerator 3 in the accelerating cavity 34.

[0105] The drift tube linear accelerator 3 of the present application connects the first coupling part 31 and the second coupling part 32 by setting a coupling member 33, thereby realizing coupling and connecting the two accelerators into a drift tube linear accelerator 3 with a complete acceleration cavity 34, effectively improving the acceleration efficiency of the drift tube linear accelerator 3 for the beam, so that the beam accelerated by the drift tube linear accelerator 3 has a higher beam energy. At the same time, the first coupling part 31, the second coupling part 32 and the coupling member 33 are coaxially arranged, and such a structural arrangement makes the structure of the drift tube linear accelerator 3 more coherent and integrated, and also makes the overall structure of the drift tube linear accelerator 3 more compact and the space utilization rate higher, thereby making the drift tube linear accelerator 3 have higher convenience and practicality. Compared with the traditional solution of multiple accelerators in series, the drift tube linear accelerator 3 of the present application effectively reduces power consumption, further reduces the cost of use, and makes the drift tube linear accelerator 3 more widely applicable. In addition, the arrangement of the drift tube support rod 333 in the present application effectively improves the structural stability of the magnet drift tube 332 , ensures the smooth flow of the beam channel, and further ensures the acceleration efficiency and effect of the drift tube linear accelerator 3 on the beam.

[0106] It should be noted that in the present application, the first coupling part 31 and the second coupling part 32 both use a cross-rod drift tube linear accelerator 3, and the arrangement of the coupling member 33 couples the two cross-rod drift tube linear accelerators 3 into a whole, and forms an accelerating cavity 34 with a resonant space and uniform electric and magnetic fields inside. Of course, in the actual production process, accelerators of other structures can also be used as coupling parts according to specific working conditions and requirements, such as: electron linear accelerators or other heavy ion accelerators, etc. Therefore, the present application does not limit this.

[0107] In the actual processing process, the coupling member 33 couples the first coupling part 31 and the second coupling part 32 to form a complete acceleration cavity 34, and forms a resonant space and a uniform electric field and magnetic field in the acceleration cavity 34. Therefore, according to the specific usage scenario and the specific needs of the user, the radius of the coupling shell 331 can be adjusted to match the resonant frequency of the first coupling part 31 and the second coupling part 32, so as to form a corresponding resonant space. Similarly, the resonant frequency of the acceleration cavity 34 and the specific distribution of the electric field and the magnetic field can also be adjusted by adjusting the radius of the shell of the first coupling part 31 and the second coupling part 32. Therefore, under actual working conditions, the radius of the first coupling part 31, the second coupling part 32 and the coupling shell 331 can be adjusted accordingly according to specific needs to adapt to the corresponding working scenario, and this application does not limit this.

[0108] Combined with reference Figure 8 In an optional embodiment, the coupling member 33 includes a water cooling pipe 335. The water cooling pipe 335 is arranged inside the magnet drift tube 332 and the drift tube support rod 333. The water cooling pipe 335 extends from the surface of the coupling housing 331 along the drift tube support rod 333 to the magnet drift tube 332, and then is distributed around the circumference of the magnet drift tube 332 and re-extends along the drift tube support rod 333 to the surface of the coupling housing 331. It can be seen from the figure that the setting of the water cooling pipe 335 connects the inside of the magnet drift tube 332, the inside of the drift tube support rod 333 and the outside of the coupling housing 331.

[0109] During the actual operation of the drift tube linear accelerator 3, since the magnet drift tube 332 passes through the high-intensity magnetic field area, the power density and heating efficiency on its surface are relatively obvious. The volume of the magnet drift tube 332 is larger than that of the drift tube 35, and the drift tube support rod 333 is also thicker, so its heating will be more obvious than that of the drift tube 35. The setting of the water-cooling pipe 335 in the present application allows the drift tube linear accelerator 3 to be fed with refrigerant from the outside of the coupling housing 331, and then enter the interior of the drift tube support rod 333 and the magnet drift tube 332 after passing through the cavity wall of the coupling housing 331, thereby cooling the drift tube support rod 333 and the magnet drift tube 332. Since only one end of the drift tube support rod 333 in the present application is connected to the inner wall of the coupling housing 331, it can be seen from the figure that the refrigerant enters the water cooling pipe 335 in the drift tube support rod 333 after passing through the cavity wall of the coupling housing 331, then flows along the water cooling pipe 335 around the magnet drift tube 332, and finally continues to flow out along the water cooling pipe 335 in the drift tube support rod 333. It can be seen that the drift tube support rod 333 of the present application can achieve self-cooling while ensuring the support strength, thereby ensuring the overall safety of the drift tube linear accelerator 3, thereby ensuring the quality of the beam and the acceleration effect and efficiency of the beam.

[0110] like Figure 1 As shown, in an optional embodiment, the coupling member 33 further includes a quadrupole magnet 336. The quadrupole magnet 336 is disposed in the magnet drift tube 332.

[0111] In actual use, when the beam passes through the flow hole 334, due to the setting of the quadrupole magnet 336, the drift tube linear accelerator 3 can constrain the beam waist within a certain range through the focusing effect of the quadrupole magnet 336, prevent the beam from diverging, and thus maintain the high density of the beam. It can be seen that the setting of the quadrupole magnet 336 enables the drift tube linear accelerator 3 to reduce the beam emittance, reduce the beam energy dispersion, and improve the collective stability of the beam, thereby improving the performance of the entire device and the beam quality. In the drift tube linear accelerator 3 of the present application, the quadrupole magnet 336 is set to two. In other optional embodiments, the number of quadrupole magnets 336 can be set according to the specific structure and requirements, for example: it can be set to a single, three, four or more. Therefore, the present application does not limit this.

[0112] It is worth mentioning that in the actual production design process, the focusing unit inside the coupling member 33 can be set accordingly according to the specific device structure and usage requirements. For example, the magnetic drift tube 332 described in this application can be used as the focusing unit, or a magnet or solenoid can be used as the focusing unit to achieve the purpose of simplifying the production process and reducing production costs. Therefore, this application does not limit this.

[0113] In an optional embodiment, six drift tubes 35 are disposed in the first coupling portion 31 , and five drift tubes 35 are disposed in the second coupling portion 32 .

[0114] As can be seen from the figure, in the first coupling part 31 and the second coupling part 32, 6 acceleration gaps 36 and 5 acceleration gaps 36 are formed between different drift tubes 35 and between the drift tube 35 and the magnet drift tube 332, respectively, for a total of 11 acceleration gaps 36. The setting of the number of drift tubes 35 in the present application avoids the situation that the overall gap voltage is too large due to too few acceleration gaps 36, thereby avoiding the situation that the voltage distribution in the cavity of the drift tube linear accelerator 3 is uneven, resulting in excessive electric field strength, vacuum breakdown, and damage to accelerator components. At the same time, it also avoids the situation that the overall length of the drift tube linear accelerator 3 is too long, the gap voltage is too small, and the acceleration efficiency is reduced due to too many drift tubes 35. It can be seen that the structural setting of the drift tube linear accelerator 3 in the present application ensures the stability and uniformity of its internal acceleration electric field, makes the gap voltage setting reasonable, and the thermal effect inside the cavity of the drift tube linear accelerator 3 is reasonably controlled, so that the quality of the beam 5 is guaranteed.

[0115] Among the six accelerating gaps 36 of the first coupling part 31, the phases of two accelerating gaps 36 are -35°, and the phases of the other four accelerating gaps 36 are 0°; and among the five accelerating gaps 36 of the second coupling part 32, the phases of two accelerating gaps 36 are -35°, and the phases of the other three accelerating gaps 36 are 0°. The accelerating gaps 36 with a phase of -35° can effectively achieve longitudinal bunching matching of the beam, while the accelerating gaps 36 with a phase of 0° can provide excellent acceleration efficiency. It can be seen that the phase setting of the accelerating gaps 36 of the drift tube linear accelerator 3 can provide a higher acceleration gradient and a better bunching effect, which effectively ensures the working efficiency of the drift tube linear accelerator 3 and also ensures the quality of the beam after being accelerated by the drift tube linear accelerator 3.

[0116] Of course, as described above, in an optional embodiment, the number of drift tubes 35 can be determined according to different structural settings and specific requirements. Therefore, different numbers of drift tubes 35 in the drift tube linear accelerator 3 will form different numbers of acceleration gaps 36, so that the proton beam can be accelerated to different energy levels. Therefore, the present application does not limit this.

[0117] In an optional embodiment, the drift tube linear accelerator 3 further includes a focusing groove 37. The location of the focusing groove 37 can be adjusted accordingly according to the structure and use requirements of the specific acceleration device 100. For example: a focusing groove 37 is arranged on the first end face so that the output end of the radio frequency quadrupole field accelerator can face the focusing groove 37, so as to better transmit the beam accelerated by the radio frequency quadrupole field accelerator to the drift tube linear accelerator 3. Alternatively, a focusing groove 37 can also be arranged on the second end face so that the beam accelerated from the drift tube linear accelerator 3 can be better focused when it is emitted. Therefore, this application does not limit this.

[0118] In an optional embodiment, the drift tube linear accelerator 3 is provided with two focusing grooves 37, which are respectively arranged on the first end surface and the second end surface. One of the focusing grooves 37 is recessed from the first end surface toward the first opening 311, and the feed hole 312 is arranged in the focusing groove 37. The other focusing groove 37 is recessed from the second end surface toward the second opening 321, and the feed hole 322 is arranged in the focusing groove 37.

[0119] The setting of the focusing groove 3717 makes the acceleration cavity 34 inside the drift tube linear accelerator 3 not a complete cylindrical structure, thereby avoiding the situation that the electromagnetic field inside the acceleration cavity 34 is unevenly distributed at the edge position close to the first end face and the second end face. It can be seen that the setting of the focusing groove 37 forms a more uniform and reasonable electric field and magnetic field inside the acceleration cavity 34, avoiding the situation that the electric field and magnetic field are concentrated at the end of the cavity. It can be seen that the setting of the focusing groove 37 ensures that a uniform electric field and magnetic field are formed inside the drift tube linear accelerator 3, ensuring the acceleration efficiency and beam quality. At the same time, the structure of the focusing groove 37 makes the acceleration device 100 more convenient and accurate during the installation process.

[0120] It should be noted that the technical solutions or technical features described in the above embodiments can be combined or supplemented with each other without causing conflicts. The scope of protection of this application is not limited to the precise structures described in the above embodiments and shown in the drawings; all modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this application should be included in the scope of protection of this application.

Claims

1. An acceleration device, characterized in that: It includes a drift tube linear accelerator and a radio frequency quadrupole accelerator; the radio frequency quadrupole accelerator is directly connected to the drift tube linear accelerator; the radio frequency quadrupole accelerator includes electrodes; wherein, Along the proton transport direction, the electrode is an integrated structure, including a regular portion and an extended portion; The extension part includes one or more bunching units, each of which has a negative synchronization phase, and the bunching capability of the radio frequency quadrupole accelerator is adjusted by setting the length, number and synchronization phase of the bunching units; The aperture and modulation factor of the beamforming unit are the same as those of the previous unit, which is a conventional unit or a beamforming unit.

2. The acceleration device according to claim 1, characterized in that: The length of the i-th bunching unit is: in: β is the relative velocity of the particles at the inlet of the bunching unit; λ is the wavelength of the incident light; φ i is the synchronization phase of the i-th beamforming unit; φ s is the synchronization phase of the previous unit of the i-th bunching unit; L pc is the length of the unit before the i-th bunching unit.

3. The acceleration device according to claim 1, characterized in that: The synchronization phase of the conventional part is -30°, and the extension part includes a first bunching unit and a second bunching unit, and the synchronization phases of the first bunching unit and the second bunching unit along the proton transmission direction are respectively -60° and -90°.

4. The acceleration device according to claim 3, characterized in that: The length of the first bunching unit is greater than or equal to 35 mm and less than or equal to 40 mm; The length of the second bunching unit is greater than or equal to 55 mm and less than or equal to 60 mm.

5. The acceleration device according to claim 1, characterized in that: The drift tube linear accelerator comprises: A first coupling part, a second coupling part and a coupling member; the coupling member is disposed between the first coupling part and the second coupling part, and couples the first coupling part and the second coupling part to enclose and form an accelerating cavity of the drift tube linear accelerator; Wherein, the coupling component includes a coupling shell, a magnet drift tube and a drift tube support rod; the coupling shell surrounds a coupling cavity of the coupling component; the magnet drift tube is arranged in the coupling cavity; the drift tube support rod is arranged in the coupling cavity and connects the magnet drift tube and the coupling shell; the magnet drift tube is coaxially arranged with the first coupling part and the second coupling part to form a beam channel of the drift tube linear accelerator in the acceleration cavity.

6. The acceleration device according to claim 5, characterized in that: The coupling member further comprises a quadrupole magnet; the quadrupole magnet is arranged in the magnet drift tube.

7. The acceleration device according to claim 5, characterized in that: The coupling member comprises a water cooling pipe; the water cooling pipe is distributed around the circumference of the magnet drift tube and extends along the drift tube support rod to the surface of the coupling housing.

8. The acceleration device according to claim 5, characterized in that: A plurality of drift tubes are arranged in the first coupling part and the second coupling part, and the plurality of drift tubes are arranged at intervals to form an acceleration gap of the drift tube linear accelerator in the acceleration cavity; Wherein, six drift tubes are arranged in the first coupling part; And / or, five drift tubes are arranged in the second coupling part.

9. The acceleration device according to claim 5, characterized in that: The drift tube linear accelerator also includes a bunching slot; The focusing groove is arranged at an end of the first coupling part away from the coupling member; the focusing groove is recessed toward the interior of the accelerating cavity; and / or, the focusing groove is arranged at an end of the second coupling part away from the coupling member; the focusing groove is recessed toward the interior of the accelerating cavity.

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