Medical compact ion accelerator

Abstract

The present disclosure provides a medical miniaturized ion accelerator, comprising: an ion source for generating low-energy ions with an initial energy; a linear accelerator for preliminarily accelerating the low-energy ions to obtain a medium-energy beam; a synchrotron for accelerating the medium-energy beam to obtain a high-energy beam with a target energy; the synchrotron comprises: two deflection units connected head-to-tail through two straight sections, for deflecting the beam in the synchrotron, and the deflection angle of each deflection unit is 180°; a focusing unit corresponding to each straight section, arranged on the straight section, for focusing the beam in the synchrotron in the horizontal direction and the vertical direction; a high-frequency accelerating cavity arranged on one straight section, for accelerating the beam in the synchrotron; an injection system arranged on the two straight sections, for introducing the medium-energy beam into the synchrotron; and a slow extraction system arranged on the two straight sections, for extracting the high-energy beam with the target energy obtained after acceleration.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of medical devices, in particular to a medical miniaturized ion accelerator. BACKGROUND

[0002] There is a physical effect called Bragg peak for ion beams (referring to hydrogen ions, helium ions, lithium ions, carbon ions and oxygen ions, etc. with mass number not more than 20 in the periodic table suitable for ion therapy), which refers to the amount of energy deposited by the ion beam in the material and the size of the energy, which reaches a peak before the ion motion stops, and then the energy deposition decreases sharply. Due to the existence of Bragg peak, ion beams can accurately kill tumor cells while causing little damage to surrounding healthy tissues. In addition, compared with conventional rays, ion beams have higher relative biological effectiveness, that is, the physical absorbed dose required to achieve the same biological effect (such as 10% survival of cells) is less than that of conventional rays, thereby significantly reducing the number of treatments for patients.

[0003] The existing ion therapy accelerator has a large floor area and high investment cost, so it is difficult to promote. The present disclosure mainly reduces the cost of the synchrotron, including reducing the number of components, reducing the manufacturing and installation cost of main components, compact structure and reducing the floor area, etc.

[0004] The existing ion therapy device (application number 201010252492.5) uses multiple dipole magnets to deflect the ion beam to form a closed track, and arranges quadrupole magnets between the dipole magnets to achieve focusing effect in horizontal and vertical directions. The existing ion therapy device has a circumference greater than 50m, and the weight of a single dipole magnet is close to 20 tons, which has high manufacturing cost and installation difficulty. Usually, a large gantry crane is needed for installation, and the space requirement is also high. Another ion therapy device (application number 202110638036.2) uses a composite superconducting magnet with a dipole field and a quadrupole field, which is more compact than the accelerator structure composed of conventional magnets. However, the extraction scheme uses vertical extraction, and the deflection iron used for extraction will introduce dispersion in the vertical direction of the high-energy beam line. Generally, the ion beam will have a certain energy dispersion, and the dispersion will make the overall size of the ion beam larger, so a special beam line is designed on the high-energy beam line to eliminate the dispersion. The introduction and elimination of dispersion can only be realized through dipole magnets. In the synchrotron, the dipole magnets are usually used to deflect the particles in the horizontal direction, so the dispersion in the horizontal direction is inherent. Therefore, whether the extraction is in the horizontal direction or in the vertical direction, the dispersion elimination in the horizontal direction is always needed on the high-energy beam line. The vertical extraction scheme increases the design and debugging difficulty of the entire high-energy beam line, because the dispersion elimination in the horizontal and vertical directions is needed at the same time. SUMMARY

[0005] In view of the above problems, the present application provides a medical miniaturized ion accelerator to solve the above problems.

[0006] One aspect of the present disclosure provides a medical miniaturized ion accelerator, comprising: an ion source for generating low-energy ions with an initial energy; a linear accelerator for preliminarily accelerating the low-energy ions to obtain a medium-energy beam; a synchrotron for accelerating the medium-energy beam to obtain a high-energy beam with a target energy; the synchrotron comprises: two deflection units connected head-to-tail by two straight sections for deflecting the beam in the synchrotron, and the deflection angle of each deflection unit is 180°; two focusing units corresponding to the straight sections one by one and arranged on the straight sections for focusing the beam in the synchrotron in the horizontal and vertical directions; a high-frequency accelerating cavity arranged on one of the straight sections for accelerating the beam in the synchrotron; an injection system arranged on the two straight sections for introducing the medium-energy beam into the synchrotron; and a slow extraction system arranged on the two straight sections for extracting the high-energy beam with the target energy obtained after acceleration.

[0007] Optionally, a stripping foil is installed between the linear accelerator and the synchrotron for converting the ions in the medium-energy beam into ions required for treatment.

[0008] Optionally, the injection system adopts multi-turn injection, and the injection system comprises: an injection slicing magnet for injecting the medium-energy beam into the synchrotron; a plurality of injection convex rail magnets arranged on the two straight sections for forming a local convex rail with gradually decreasing height, adjusting the horizontal acceptance of the synchrotron to the outlet of the injection electrostatic deflection plate; and an injection electrostatic deflection plate arranged on one of the two straight sections and connected to the injection slicing magnet for giving the medium-energy beam a transverse kick angle to enter the horizontal acceptance of the synchrotron and gradually fill the entire horizontal acceptance with the decrease of the convex rail.

[0009] Optionally, the slow extraction system comprises: an extraction electrostatic deflection plate and an extraction slicing magnet arranged on the two straight sections adjacent to the focusing units, and the phase shift between the extraction electrostatic deflection plate and the extraction slicing magnet is 270° for extracting the high-energy beam with the target energy obtained after acceleration.

[0010] Optionally, each focusing unit comprises three quadrupole magnets.

[0011] Optionally, the slow extraction system comprises a plurality of extraction convex rail magnets arranged on the two linear sections to form a local convex rail at the extraction electrostatic deflector, so that the beam in the synchrotron is close to the pole plate of the extraction electrostatic deflector.

[0012] Optionally, the slow extraction system further comprises two resonance sextupole magnets symmetrically arranged on the two linear sections and adjacent to the quadrupole magnet at one end of the focusing unit on the corresponding linear section, for causing the third-order resonance of the beam in the synchrotron and forming a stable triangle in the phase space; two chromaticity correction sextupole magnets symmetrically arranged on the two linear sections and adjacent to the quadrupole magnet at the other end of the focusing unit on the corresponding linear section, for adjusting the chromaticity to make the extraction phase diagram of particles of different energies in the synchrotron overlap, thereby improving the extraction efficiency; and an extraction excitation (12) arranged on a section of the linear section, for generating a transverse high-frequency electric field to make the amplitude of the particle motion larger, gradually leave the stable triangle and be extracted.

[0013] Optionally, each deflection unit is composed of a plurality of superconducting secondary magnets.

[0014] Optionally, the ion source is an electron cyclotron resonance ion source.

[0015] Optionally, the linear accelerator comprises a radio frequency quadrupole field accelerator for accelerating the low-energy ions extracted from the ion source to an energy level of 0.6 MeV / u; and a drift tube linear accelerator for accelerating the low-energy ions accelerated by the radio frequency quadrupole field accelerator to an energy level of 4-7 MeV / u.

[0016] The above at least one technical solution adopted in the embodiments of the present disclosure can achieve the following beneficial effects:

[0017] The medical small-sized ion accelerator provided by the embodiments of the present disclosure reduces the number of components in the synchrotron as much as possible, concentrates the components outside the dipole magnets on the two linear sections, greatly improves the space utilization, shortens the circumference of the accelerator, and the overall circumference is not greater than 30 meters. The medical small-sized ion accelerator provided by the embodiments of the present disclosure has small land occupation and low construction cost, and the unique optical design makes the aperture of the dipole magnet small, effectively controls the manufacturing cost and power consumption of the dipole magnet. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more completely understand the present disclosure and its advantages, reference will now be made to the following description taken together with the accompanying drawings, in which:

[0019] Figure 1 A schematic diagram of a small-sized heavy ion synchrotron provided by the embodiments of the present disclosure is schematically shown;

[0020] Figure 2The envelope functions and dispersion functions of the synchrotron in horizontal and vertical directions are schematically shown;

[0021] Figure 3 The trajectory diagram of the beam injection process is schematically shown;

[0022] Figure 4 The trajectory diagram of the beam injection process is schematically shown; Figure 2 The trajectory diagram of the beam injection process is schematically shown;

[0023] Figure 5 The trajectory diagram of the beam injection process is schematically shown;

[0024] Reference signs:

[0025] 1 - ion source; 2 - linear accelerator; 3 - synchrotron; 4 - deflection unit; 5 - high frequency accelerating cavity; 6 - stripping film; 7 - injection slicing magnet; 8 - injection electrostatic deflection plate; 9 - injection convex rail magnet; 10 - extraction electrostatic deflection plate; 11 - extraction slicing magnet; 12 - extraction excitation; 13 - quadrupole magnet; 14 - extraction convex rail magnet; 15 - resonance sextupole magnet; 16 - chromaticity correction sextupole magnet. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It is to be understood, however, that the description is merely exemplary and is not intended to limit the scope of the present disclosure. In the following detailed description of the embodiments of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present disclosure. However, it would be apparent to those skilled in the art that the embodiments of the present disclosure can be practiced without these specific details. In other instances, well-known structures and

[0027] The terms used herein are merely used to describe specific embodiments and are not intended to limit the present disclosure. The terms "include", "comprise" and the like used herein indicate the presence of the described features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0028] All terms used herein, including technical and scientific terms, have the same meanings as those generally understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having meanings consistent with the context of the present description, and should not be interpreted in an idealized or excessively formal manner.

[0029] As Figure 1As shown, this disclosure provides a miniaturized medical ion accelerator, including an ion source 1, a linear accelerator 2, and a synchrotron 3. The ion source 1 is used to generate low-energy ions with initial energy; the linear accelerator 2 is used to initially accelerate the low-energy ions to obtain a medium-energy beam; and the synchrotron 3 is used to accelerate the medium-energy beam to obtain a high-energy beam with a target energy.

[0030] Ion source 1 employs a conventional electron cyclotron resonance ion source, but a laser ion source can also be used. Laser ion sources are a novel type of ion source that generates multi-charged ion beams, characterized by high current intensity and short beam pulse time; however, the overall technology is more complex and currently not mature. In this embodiment, ion source 1 employs an electron cyclotron resonance ion source.

[0031] The linear accelerator 2 includes: a radio frequency quadrupole accelerator for accelerating low-energy ions extracted from ion source 1 to an energy level of 0.6 MeV / u; and a drift tube linear accelerator for accelerating low-energy ions accelerated by the radio frequency quadrupole accelerator to an energy level of 4-7 MeV / u.

[0032] A stripping membrane 6 is installed between the linear accelerator 2 and the synchrotron 3 to convert the ions in the medium-energy beam into ions required for treatment. The linear accelerator 2 can accelerate different types of ions provided their charge-to-mass ratios are similar; commonly used ions for treatment include protons (H+). + or carbon ions 12 C 6+ Because of their different charge-to-mass ratios, they cannot be accelerated using the same linear accelerator 2. Therefore, ion source 1 typically produces ions with different mass-to-charge ratios. 3 H + , 12 C 4+ Ions with the same charge-to-mass ratio are accelerated and then converted into H+ by the stripping membrane 6. + or 12 C 6+ .

[0033] like Figure 1 As shown, the synchrotron 3 includes: two deflection units 4, two focusing units, a high-frequency acceleration cavity 5, an injection system, and a slow extraction system.

[0034] Two deflection units 4 are connected end-to-end by two straight sections to deflect the beam in the synchrotron 3. Each deflection unit 4 has a deflection angle of 180°. The deflection unit 4 can be composed of one or more superconducting diodes. Large-angle superconducting diodes are difficult to fabricate, while multiple small-angle diodes would make the entire deflection unit 4 too large. In this embodiment, each deflection unit 4 is composed of multiple superconducting diodes, and a preferred embodiment is as follows: Figure 1The superconducting dipole magnets are inclined solenoid type dipole magnets, which have the characteristics of high magnetic field strength and easy combination of various magnetic fields. The dipole field is generated by two layers of coils, and the quadrupole field is generated by two layers of coils outside the two layers of coils.

[0035] In a less preferred solution, the quadrupole field in the deflection unit can also be realized by independent quadrupole magnets, thereby reducing the design difficulty of the superconducting dipole magnets, but slightly increasing the circumference of the entire accelerator.

[0036] Figure 2 The envelope functions (β functions) and dispersion functions in the horizontal and vertical directions of the synchrotron 3 are shown. The envelope functions and dispersion functions jointly determine the transverse size of the beam in the synchrotron 3. The beam envelope in the synchrotron 3 is generally represented as:

[0037]

[0038] wherein ε represents the emittance of the beam, and σ represents the momentum spread of the beam.

[0039] The processing difficulty of the superconducting dipole magnets is positively correlated with the size of the superconducting dipole magnets. The design of the embodiment of the present disclosure makes the envelope function in the dipole magnets small, so that the beam size in the dipole magnets is small, which is conducive to reducing the size of the superconducting dipole magnets and reducing the processing difficulty.

[0040] The focusing units correspond to the straight sections one by one and are arranged on the straight sections. In the embodiment, each focusing unit includes three quadrupole magnets 13. The quadrupole field in the focusing unit is used to cooperate with the quadrupole field in the deflection unit to realize the focusing of the beam in the horizontal direction and the vertical direction.

[0041] The high-frequency accelerating cavity 5 is arranged on a straight section and is used to accelerate the beam in the synchrotron 3. In actual applications, the high-frequency accelerating cavity 5 can accelerate or decelerate the beam. The beam in the synchrotron 3 first passes through the high-frequency adiabatic trapping to form a beam bunch. By adjusting the frequency of the high-frequency accelerating cavity 5 and the rising speed of the magnetic field, the periodic motion of the beam bunch and the periodic change of the accelerating electric field can be kept strictly synchronized, and the beam bunch can keep a constant orbit to continuously accelerate or decelerate.

[0042] The injection system is arranged on the two straight sections and is used for introducing the medium-energy beam into the synchrotron 3. The injection modes of the synchrotron 3 generally include single-turn injection, multi-turn injection, stripping injection and the like. The single-turn injection involves less equipment, and the required beam acceptance of the synchrotron is smaller because of only one injection, but the requirement of the injector is higher for the same ion number. The multi-turn injection has a smaller beam gain due to the Liouville theorem, and generally only has a gain of more than ten times, but is suitable for injection of different kinds of ions. The stripping injection can break through the Liouville theorem by stripping the ions in a low charge state into particles in a high charge state for injection, and realizes a gain of more than 50 times, but can only inject one kind of ion. In order to make the synchrotron suitable for accelerating different ions and reduce the technical difficulty, the injection mode of the multi-turn injection is adopted in the application.

[0043] In the embodiment, the injection system comprises an injection cutting magnet 7, an injection electrostatic deflection plate 8 and a plurality of injection convex rail magnets 9. The injection cutting magnet 7 is used for injecting the medium-energy beam into the synchrotron 3. The plurality of injection convex rail magnets 9 are arranged on the two straight sections and are used for forming a local convex rail with gradually descending height, and adjusting the horizontal acceptance of the synchrotron 3 to the outlet of the injection electrostatic deflection plate 8. The injection electrostatic deflection plate 8 is arranged on one of the two straight sections, is connected with the injection cutting magnet 7, and is used for giving the medium-energy beam a transverse kick angle so that the medium-energy beam enters the horizontal acceptance of the synchrotron 3 and gradually fills the whole horizontal acceptance along with the descending of the convex rail. As shown in FIG. 2, the beam is continuously injected, and finally fills the whole horizontal acceptance of the synchrotron along with the gradually descending of the strength of the injection convex rail magnet 9, thereby completing the injection of the beam. Optionally, the number of the injection convex rail magnets 9 can be 2-4, and preferably 3. Figure 3

[0044] The slow extraction system is arranged on the two straight sections and is used for extracting the high-energy beam of the target energy after acceleration. In the embodiment, the slow extraction system comprises an extraction electrostatic deflection plate 10, an extraction cutting magnet 11, three extraction convex rail magnets 14, two resonance sextupole magnets 15, two chromaticity correction sextupole magnets 16 and an extraction kicker 12.

[0045] The extraction electrostatic deflection plate 10 and the extraction cutting magnet 11 are arranged on the two straight sections and are adjacent to the focusing unit. The phase shift of the extraction electrostatic deflection plate 10 and the extraction cutting magnet 11 is 270°, and the extraction electrostatic deflection plate 10 and the extraction cutting magnet 11 are used for extracting the high-energy beam of the target energy after acceleration.

[0046] The plurality of extraction convex rail magnets 14 are arranged on the two straight sections and are used for forming a local convex rail at the extraction electrostatic deflection plate, so that the beam in the synchrotron 3 is close to the pole plate of the extraction electrostatic deflection plate 10 on the local convex rail, and is on the central orbit outside the local convex rail, which is beneficial to reduce the envelope of the extracted beam, ensure the extraction efficiency, and also avoid the loss of the beam on the electrostatic deflection plate during the injection and acceleration process.​Figure 4 The shown is the extraction convex rail, and the position of the picture starting point is the entrance position of the electrostatic deflection plate. Optionally, the number of the extraction convex rail magnets can be 2-4, preferably 3.

[0047] Two resonance sextupole irons 15 are symmetrically arranged on two linear sections and adjacent to the quadrupole magnets 13 at one end of the focusing unit on the corresponding linear section, for causing the third-order resonance of the beam in the synchrotron 3 and forming a stable triangle in the phase space. When the amplitude increases to a certain extent, the particles enter the electrostatic deflection plate, and then pass through the extraction cut iron for extraction. The extraction excitation 12 generates a transverse high-frequency electric field to continuously increase the amplitude of the particles originally located in the stable triangle and further leave the stable region, so that the beam extraction is continuously and stably carried out.

[0048] Two chromaticity correction sextupole irons 16 are symmetrically arranged on two linear sections and adjacent to the quadrupole magnets 13 at the other end of the focusing unit on the corresponding linear section, for adjusting the chromaticity to make the extraction phase diagram of the particles of different energies in the synchrotron 3 overlap, thereby satisfying the hardt condition and improving the extraction efficiency.

[0049] The extraction excitation 12 is arranged on a linear section, for generating a transverse high-frequency electric field to increase the amplitude of the particle motion, gradually leave the stable triangle and be extracted.

[0050] Figure 5 The trajectory diagram is the trajectory of the last three turns of the beam before extraction and the trajectory after entering the electrostatic deflection plate. Unlike the electrostatic deflection plate and the extraction cut magnet 11 in the medical synchrotron, which are generally arranged with a phase shift of nearly 90°, the electrostatic deflection plate and the extraction cut magnet 11 in the embodiment of the present disclosure are respectively arranged on the opposite long linear sections, and the phase shift therebetween is nearly 270°. In the extraction design, it is generally necessary to consider the distance between the deflected extraction beam passing through the electrostatic deflection plate and the circulating beam at the entrance of the cut magnet, which is used to install the pole plate of the cut magnet. Theoretically, the size of the distance depends on the thickness of the magnetic pole, and determines the deflection angle of the electrostatic deflection plate,

[0051]

[0052] wherein, θ is the kick angle of the electrostatic deflection plate, β ES is the horizontal envelope function at the electrostatic deflection plate, β MS is the horizontal envelope function at the cut magnet, (μ MS -μ ES) is to cut the phase shift between the magnet and the electrostatic deflection plate. In this design, the electrostatic deflection plate and the extraction cut magnet 11 are close to the horizontal focusing quadrupole magnet 13, so that the β function of the position where they are located will be a maximum value. By optimizing the distribution of the β function, the phase shift between the electrostatic deflection plate and the cut magnet can be about 270°. According to the formula, this design can greatly increase the distance gap between the extraction beam and the circulating beam, so as to reduce the requirements on the extraction element, thereby reducing the size of the extraction element while stably extracting the beam current.

[0053] According to the above scheme, the medical small ion accelerator provided by the embodiment of the present disclosure reduces the number of components in the synchrotron as much as possible, concentrates the components outside the dipole on two straight-line sections, greatly improves the space utilization, shortens the circumference of the accelerator, and the overall circumference is not greater than 30 meters. The medical small ion accelerator has small land occupation and low construction cost, and the unique optical design makes the aperture of the dipole small, effectively controls the manufacturing cost and power consumption of the dipole.

[0054] Those skilled in the art can understand that the features described in various embodiments and / or claims of the present disclosure can be combined or / and combined, even if such combinations or combinations are not explicitly described in the present disclosure. In particular, the features described in various embodiments and / or claims of the present disclosure can be combined and / or combined in various combinations without departing from the spirit and teachings of the present disclosure. All these combinations and / or combinations fall within the scope of the present disclosure.

[0055] Although the present disclosure has been shown and described with reference to certain exemplary embodiments thereof, it should be understood by those skilled in the art that various changes in form and detail can be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents. Therefore, the scope of the present disclosure should not be limited to the above-described embodiments, but should be determined only by the appended claims, and should be defined by the equivalents of the appended claims.

Claims

1. A miniaturized medical ion accelerator, characterized by, The application relates to a medical ion source, which comprises the following components: an ion source (1) for generating low-energy ions with initial energy; a linear accelerator (2) for preliminarily accelerating the low-energy ions to obtain a medium-energy beam; a synchrotron (3) for accelerating the medium-energy beam to obtain a high-energy beam with target energy; the synchrotron (3) comprises: two deflection units (4) connected in sequence through two linear sections, for deflecting the beam in the synchrotron (3), and the deflection angle of each deflection unit (4) is 180 DEG; two focusing units corresponding to the linear sections, arranged on the linear sections, for focusing the beam in the synchrotron (3) in horizontal and vertical directions; a high-frequency accelerating cavity (5) arranged on one linear section, for accelerating the beam in the synchrotron (3); an injection system arranged on the two linear sections, for introducing the medium-energy beam into the synchrotron (3); a slow extraction system arranged on the two linear sections, for extracting the high-energy beam with target energy obtained after acceleration; the injection system adopts multi-turn injection, and the injection system comprises an injection cutting magnet (7) for injecting the medium-energy beam into the synchrotron (3); a plurality of injection convex rail magnets (9) arranged on the two linear sections, for forming a local convex rail with gradually descending height, and adjusting the horizontal acceptance of the synchrotron (3) to the outlet of an injection electrostatic deflection plate (8); the injection electrostatic deflection plate (8) is arranged on one of the two linear sections, connected with the injection cutting magnet (7), for giving the medium-energy beam a transverse kick angle, so that the medium-energy beam enters the horizontal acceptance of the synchrotron (3) and gradually fills the whole horizontal acceptance along with the descending convex rail; the slow extraction system comprises an extraction electrostatic deflection plate (10) and an extraction cutting magnet (11), arranged on the two linear sections and adjacent to the focusing units, and the phase shift between the extraction electrostatic deflection plate (10) and the extraction cutting magnet (11) is 270 DEG, for extracting the high-energy beam with target energy obtained after acceleration.

2. The compact medical ion accelerator according to claim 1, wherein A stripping film (6) is arranged between the linear accelerator (2) and the synchrotron (3), for converting the ions in the medium-energy beam into ions required for treatment.

3. The compact medical ion accelerator according to claim 1, wherein Each focusing unit comprises three quadrupole magnets (13).

4. The compact medical ion accelerator according to claim 3, wherein The slow extraction system comprises: a plurality of extraction convex rail magnets (14) arranged on the two linear sections, for forming a local convex rail at the extraction electrostatic deflection plate (10), so that the beam in the synchrotron (3) approaches the pole plate of the extraction electrostatic deflection plate (10).

5. The compact medical ion accelerator according to claim 4, wherein The slow extraction system further comprises: two resonance sextupole magnets (15) symmetrically arranged on the two linear sections and adjacent to the quadrupole magnets (13) at one end of the focusing units on the corresponding linear sections, for causing the third-order resonance of the beam in the synchrotron (3) and forming a stable triangle in the phase space. Two sextupole magnets (16) are symmetrically arranged on the two linear sections and adjacent to the quadrupole magnets (13) at the other end of the focusing units on the corresponding linear sections, for adjusting the chromaticity to make the particle extraction phase diagrams of different energies in the beam of the synchrotron (3) overlap, thereby improving the extraction efficiency; An extraction kicker (12) is arranged on a section of the linear section to generate a transverse high-frequency electric field to make the amplitude of the particle motion larger, so that the particles gradually leave the stable triangle and are extracted.

6. The compact medical ion accelerator according to claim 1, wherein Each of the deflection units (4) is composed of a plurality of superconducting second-order magnets.

7. The compact medical ion accelerator according to claim 1, wherein The ion source (1) is an electron cyclotron resonance ion source.

8. The compact medical ion accelerator according to claim 1, wherein The linear accelerator (2) comprises: A radio frequency quadrupole field accelerator for accelerating the low-energy ions extracted from the ion source (1) to an energy level of 0.6 MeV / u; A drift tube linear accelerator for accelerating the low-energy ions accelerated by the radio frequency quadrupole field accelerator to an energy level of 4-7 MeV / u.

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