A conduction-cooled superconducting synchrotron accelerator system for proton therapy

Abstract

The present invention discloses a conduction-cooled superconducting synchrocyclotron system for proton therapy, belonging to the technical field of particle accelerators. It includes a main magnet system, a conduction-cooled superconducting magnet system, a high-frequency system, an ion source system, a central region system, an extraction system and a vacuum system. The main magnet system includes a yoke and a cylindrical magnetic pole arranged inside the yoke. The surface of the pole tip of the magnetic pole has a modulation curve that descends radially to form a weak focusing magnetic field, and the field index n satisfies 0 < n < 1. The conduction-cooled superconducting magnet system includes a high-field superconducting coil, and the high-field superconducting coil is coaxially arranged outside the magnetic pole of the main magnet system. It can achieve the use of the synchrocyclotron acceleration mechanism and the pulsed beam extraction method, accurately control the average beam intensity at the nanoampere level, reduce beam loss from the source, effectively save the capital construction cost, and at the same time reduce the radiation risk of operation and maintenance personnel and the equipment downtime cooling time.

Description

Technical Field

[0001] This invention belongs to the field of particle accelerator technology, and more specifically, relates to a conduction-cooled superconducting synchrotron accelerator system for proton therapy. Background Technology

[0002] Proton therapy, with its unique Bragg peak physics effect, can precisely concentrate high-dose radiation on the tumor target area while reducing damage to surrounding normal tissues. It has become an important development direction of modern radiotherapy. In this treatment system, the proton accelerator is the core device for generating and delivering the therapeutic beam, and its performance directly determines the safety, effectiveness and economy of the treatment.

[0003] Currently, commercial proton therapy systems generally use superconducting isochronous cyclotron accelerators as the radiation source. Although these accelerators can provide continuous and high-intensity proton beams, the spiral sector magnetic pole structure designed to achieve isochronous acceleration is extremely complex and requires stringent processing precision, resulting in high magnet manufacturing costs. This has become one of the key factors restricting the widespread adoption of the equipment. A more prominent problem is that the microampere-level beam intensity generated far exceeds the nanoampere level required for actual treatment. The large amount of excess beam interacts with the equipment materials during acceleration, scraping, and transmission, producing significant high-energy neutron radiation. This triggers severe induced radioactive activation of the accelerator's structural components. This not only forces the construction of exceptionally thick concrete shielding walls in the treatment room to ensure safety, significantly increasing infrastructure costs, but also results in a long cooling time after the equipment is shut down, greatly increasing the radiation exposure risk for maintenance personnel and the complexity of operation and maintenance.

[0004] As another technical approach, superconducting synchrotron accelerators adopt the principle of weak focusing, which greatly simplifies their magnetic pole structure. However, traditional superconducting synchrotron accelerators usually rely on liquid helium immersion cooling to maintain the operation of superconducting coils. This liquid helium cooling system is not only large in size and complex in supporting facilities, but also comes with potential safety risks such as liquid helium leakage and loss of quench, and has high maintenance requirements, which is also not conducive to its widespread deployment in medical settings. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a conduction-cooled superconducting synchrotron accelerator system for proton therapy. This system can achieve precise control of the average beam intensity at the nanoampere level by using a synchrotron acceleration mechanism and a pulsed beam extraction method, thereby reducing beam loss from the source, effectively saving infrastructure costs, and reducing the radiation risk to maintenance personnel and equipment downtime for cooling.

[0006] To solve the above problems, the present invention adopts the following technical solution:

[0007] A conduction-cooled superconducting synchrotron accelerator system for proton therapy includes a main magnet system, a conduction-cooled superconducting magnet system, a high-frequency system, an ion source system, a central region system, an extraction system, and a vacuum system.

[0008] The main magnet system includes a yoke and cylindrical magnetic poles disposed within the yoke. The pole tip surface of the cylindrical magnetic poles has a modulation curve that descends radially to form a weakly focused magnetic field, and the field index n satisfies 0. <n<1;

[0009] The conductive cooling type superconducting magnet system includes a high magnetic field superconducting coil, which is coaxially arranged around the cylindrical magnetic poles of the main magnet system to provide a background magnetic field for the accelerator.

[0010] The high-frequency system includes a radio frequency cavity and a rotating capacitor. The radio frequency cavity is disposed in the gap between the cylindrical magnetic poles. The rotating capacitor is electrically connected to the radio frequency cavity and is used to periodically adjust the capacitance of the resonant circuit so that the frequency change of the high-frequency voltage is synchronized with the cyclotron frequency of the proton beam.

[0011] The ion source system includes a cold cathode Penning ion source, which is located at the center of the accelerator;

[0012] The central region system includes a suction electrode, which is disposed in the central region of the radio frequency cavity;

[0013] The extraction system is located at the edge region of the cylindrical magnetic pole and is used to extract the proton beam accelerated to the target energy.

[0014] The vacuum system includes a vacuum pump and a vacuum pipe, the vacuum pipe being connected to the magnetic yoke, and the main magnet system forming a vacuum chamber inside.

[0015] Furthermore, the main magnet system also includes magnetic field pads and magnetic field pads, which are disposed on the surface of the cylindrical magnetic pole for local adjustment of the magnetic field.

[0016] Furthermore, the conductive cooling superconducting magnet system also includes a multi-stage refrigerator, a cryostat, and a heat-conducting component; the strong magnetic field superconducting coil is disposed inside the cryostat; one end of the heat-conducting component is connected to the cold head of the refrigerator, and the other end passes through the cryostat and is connected to the support frame of the strong magnetic field superconducting coil.

[0017] Furthermore, the rotating capacitor includes a fixed plate and a movable plate driven by a servo motor, and the capacitance is periodically changed by the rotation of the movable plate.

[0018] Furthermore, the pulse beam emission timing of the ion source system is phase-locked with the frequency modulation period of the rotating capacitor.

[0019] Furthermore, the extraction system includes a regenerator, a magnetic channel, and a quadruple lens assembly; the regenerator is a ferromagnetic protrusion disposed on the edge of the cylindrical magnetic pole; the magnetic channel is composed of multiple hollow channel units made of passive soft magnetic material connected in sequence and embedded in the magnetic yoke; the quadruple lens assembly is disposed at the outlet of the magnetic channel.

[0020] Furthermore, the vacuum chamber boundary of the vacuum system is formed by the magnetic yoke inner cavity of the main magnet system and the cryogenic thermostat outer shell of the conductive cooling superconducting magnet system sealed by a sealing ring.

[0021] Furthermore, it also includes a lifting system, which includes a hydraulic lifting assembly, the fixed end of which is connected to the lower half-yoke and the main support assembly, and the movable end of which is connected to the upper half-yoke.

[0022] Furthermore, the central magnetic field strength generated by the high magnetic field superconducting coil is not less than 5T, and the accelerator system can extract a proton beam with an energy of not less than 210MeV.

[0023] Furthermore, the heat-conducting component is a flexible cooling strip made of high-purity aluminum or oxygen-free copper; the strong magnetic field superconducting coil is made of NbTi or... Superconducting wire winding.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) This scheme adopts a synchronous cyclotron acceleration mechanism and a pulsed beam extraction method to precisely control the average beam intensity at the nanoampere level. Compared with the microampere excess beam of traditional isochronous accelerators, it reduces beam loss from the source. This significantly reduces the neutron yield and component activation level inside the equipment, allowing the thickness of the radiation shielding wall in the treatment room to be reduced, effectively saving infrastructure costs, while reducing the radiation risk to maintenance personnel and the equipment downtime cooling time.

[0026] (2) The main magnet of this scheme adopts a disc-shaped weak focusing magnetic pole structure without spiral fan shape. The magnetic field modulation is achieved only through the precision machining of the pole head, which completely avoids the manufacturing difficulties of complex three-dimensional curved surfaces. This design can be processed using conventional CNC machine tools, while simplifying the production cycle and process.

[0027] (3) This scheme uses a multi-stage refrigerator in conjunction with a high thermal conductivity metal strip to directly cool the superconducting coil, completely eliminating the liquid helium Dewar and complex recovery pipeline system. This not only eliminates the potential safety risks caused by liquid helium leakage and loss of quench, but also makes the daily operation and maintenance of the accelerator like ordinary electromechanical equipment, without the need for a dedicated helium operation team and facilities, which significantly reduces the operational complexity and cost throughout the entire life cycle.

[0028] (4) This scheme reduces the proton cyclotron radius by using a superconducting strong magnetic field and combines a highly integrated magnetic yoke and vacuum chamber design to achieve a compact layout of the whole machine. This miniaturized design greatly reduces the accelerator's footprint and makes it easier to install and lay out in existing hospital buildings, reducing the stringent requirements of the proton therapy center for site space. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0030] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0031] Figure 2 This is a cross-sectional schematic diagram of the present invention;

[0032] Figure 3 This is a schematic diagram of the main magnet system of the present invention;

[0033] Figure 4 This is a schematic diagram of the structure of the high-frequency system of the present invention;

[0034] Figure 5 This is a schematic diagram of the structure of the central system area of ​​the present invention;

[0035] Figure 6 This is a schematic diagram of the structure of the system leading out in this invention.

[0036] Explanation of the labels in the diagram:

[0037] 101. Support assembly; 102. Hydraulic lifting assembly; 103. Magnetic yoke; 104. Axial tie rod; 105. Radial tie rod;

[0038] 201. Cylindrical magnetic pole; 202. Pole head; 203. Magnetic field pad strip; 204. Magnetic field pad block;

[0039] 301. Rotating capacitor; 302. Tuner; 303. Radio frequency cavity;

[0040] 401. Beam blocker; 402. Beam channel; 403. Absorber; 404. Cold cathode Penning ion source;

[0041] 501. Graphite beam cutter; 502. Magnetic channel 1; 503. Magnetic channel 2; 504. Magnetic channel 3; 505. Magnetic channel 4; 506. Quadrupole lens assembly; 507. Regenerator; 508. Harmonic extraction coil. Detailed implementation manners

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0043] Embodiment 1

[0044] Figures 1 to 3 The overall structure of a conduction-cooled superconducting synchrocyclotron system for proton therapy provided by a preferred embodiment of the present invention is shown. The system mainly consists of a main magnet system, a conduction-cooled superconducting magnet system, a high-frequency system, an ion source and central region system, an extraction system, a vacuum system, and a lifting system. The entire device has a compact structure and high integration.

[0045] I. Overall system configuration and main magnet system

[0046] The entire accelerator has a cylindrical structure symmetric in the up-down direction. Its support frame is the main support assembly 101 of the accelerator, which is used to fix the whole machine. The main magnet system, as the mechanical main body and magnetic circuit core, includes a heavy magnetic yoke 103 made of forged steel, a cylindrical magnetic pole 201, and a pole tip 202 with a modulation curve. The magnetic yoke 103 forms a closed magnetic flux loop. The cylindrical magnetic pole 201 is precisely fixed and positioned on the midplane inside the magnetic yoke 103 through an axial tie rod 104 and a radial tie rod 105.

[0047] The key innovation of this embodiment lies in the design of the cylindrical magnetic pole 201. Its pole tip 202 is in the shape of a round cake, abandoning the complex and expensive spiral sector structure in traditional isochronous cyclotrons. The working surface of the pole tip 202 is machined by a high-precision numerical control machine tool to form a specific radially decreasing curve. This radially decreasing curve is configured such that the magnetic field B on the midplane decreases with the increase of the radius r and satisfies the weak focusing condition, that is, the field index n satisfies 0 < n < 1, where the field index n is defined as: ;

[0048] This magnetic field distribution can provide axial and radial focusing forces for the proton beam during the acceleration process without additional focusing coils. For example, in a specific embodiment, it is designed to be approximately 7.1 T from the center to the edge, and the edge magnetic field smoothly decreases to approximately 6.0 T as the radius increases. The corresponding field index n remains within the range of 0 < n < 1 in the acceleration region. Those skilled in the art can determine the specific radial descent profile curve of the working surface of the pole tip 202 according to the above distribution requirements of the field index n through electromagnetic field simulation calculations, which greatly simplifies the magnet structure and reduces the manufacturing cost. To finely adjust the magnetic field, magnetic field trimming bars 203 and magnetic field trimming blocks 204 are also provided on the surface of the cylindrical magnetic pole 201 for optimizing the magnetic field isochronism and reducing harmonic components.

[0049] II. Conductive-cooled superconducting magnet system

[0050] As Figure 2 and Figure 3 shown, the conductive-cooled superconducting magnet system is integrated inside the main magnet system. The high-field superconducting coil is concentrically arranged in the coil space outside the cylindrical magnetic pole 201. The coil is wound with NbTi or superconducting wire and is encapsulated in a cryostat.

[0051] This system adopts the direct conduction cooling method with zero liquid helium. Specifically, the system is equipped with multiple, for example, 4 to 6 G-M cycle or pulse tube refrigerators, collectively referred to as a multi-stage refrigeration unit. The second-stage cold head operates in the 4K temperature range. Through flexible cold conduction belts made of high-purity oxygen-free copper or high-purity aluminum, as high-thermal-conductivity conduction components, the cold quantity of the cold head of the refrigerator is directly and efficiently conducted to the support skeleton of the superconducting coil or the coil winding itself. The heat generated during the operation of the coil, such as AC loss and joint heat, is removed through solid heat conduction, thereby maintaining the coil temperature below the superconducting transition temperature, for example, approximately 4.2K. The entire inside of the cryostat maintains a high vacuum and is wrapped with multiple layers of super-insulating materials to minimize heat leakage to the greatest extent. This design completely eliminates the large liquid helium dewar, complex liquid helium transfer pipelines, and re-liquefaction system, eliminates the safety risks that may be caused by liquid helium leakage and quench, and simplifies operation and maintenance.

[0052] III. High-frequency system

[0053] As Figure 4 shown, the high-frequency system is used to generate an accelerating electric field. The radio frequency cavity 303 installed in the gap of the cylindrical magnetic pole 201 forms a pair of Dee-shaped electrodes inside the radio frequency cavity 303. One is the high-voltage Dee, and the other is the grounded dummy Dee, and an accelerating gap is formed between the two.

[0054] Because this system uses a weak focusing magnetic field, meaning the magnetic field decreases with the radius, and the proton energy increases, leading to an increase in relativistic mass, the proton's cyclotron frequency will continuously decrease during acceleration. Therefore, the high-frequency system must operate in frequency conversion mode. The component that realizes frequency conversion is the rotating capacitor 301, which is electrically connected to the end of the radio frequency cavity 303 via a coaxial transmission line. The rotating capacitor 301 consists of a set of fixed plates and a set of moving plates driven by a servo motor to rotate at high speed. By precisely controlling the rotation angle and speed of the moving plates, the equivalent capacitance of the resonant circuit can be changed periodically and continuously, thereby causing the resonant frequency of the radio frequency cavity 303, i.e., the frequency of the accelerating voltage, to change according to a preset curve. This frequency change curve is designed to be precisely synchronized with the falling curve of the proton's cyclotron frequency in the specific weak focusing magnetic field of this embodiment, ensuring that the particle is always in the accelerating phase throughout the entire acceleration process.

[0055] To compensate for the slight frequency drift caused by factors such as temperature and mechanical stress, and to achieve precise closed-loop control of the frequency, the high-frequency system is also equipped with a tuner 302. The tuner 302, for example, a movable piston type or blade type tuner, is also electrically connected to the radio frequency cavity 303 and located in the resonant circuit. Driven by a stepper motor or piezoelectric ceramic, it can quickly and finely adjust the capacitance or inductance within a small range, thereby locking the actual operating frequency of the high-frequency system at the set target value. The rotating capacitor 301 is responsible for large-range, periodic frequency scanning, while the tuner 302 is responsible for real-time fine-tuning based on this. The two work together to ensure the high stability and reliability of the acceleration process.

[0056] IV. Ion Source System and Central Region System

[0057] like Figure 5 As shown, the ion source and central region system are located at the geometric center of the accelerator. The ion source adopts a built-in cold cathode Penning ion source 404, the main body of which is inserted into the central position from below or to the side of the magnetic yoke 103 through a radial gas lock mechanism.

[0058] The central region system includes an absorber 403 fixed at the center of the high-voltage Dee electrode, a beam channel 402, and a beam blocker 401. Under the action of a high-frequency voltage of a specific phase, the absorber 403 pulls protons generated by the cold cathode Penning ion source 404 out of the plasma. The beam channel 402 and the beam blocker 401 perform geometric selection and restriction on the initial beam to ensure that only qualified particles are injected into the first acceleration orbit, thereby improving the beam injection efficiency.

[0059] An important control feature is that the ignition of the cold cathode Penning ion source 404, i.e. the timing of generating a pulsed proton beam, is strictly phase-locked with the frequency scanning period of the aforementioned rotating capacitor 301. The control system only triggers the cold cathode Penning ion source 404 to generate a short pulse beam when the frequency of the rotating capacitor 301 scans to a frequency window that can effectively capture and accelerate particles. This on-demand beam supply mechanism controls the average beam intensity of the accelerator to the nanoampere level from the source.

[0060] V. Extraction System

[0061] like Figure 6 As shown, the extraction system is located at the edge radius of the cylindrical magnetic pole 201 and is used to extract the proton beam accelerated to its final energy, such as 210 MeV, from the main acceleration region. This system includes:

[0062] Regenerator 507: consists of several ferromagnetic metal blocks, such as industrial pure iron, embedded on the edge of cylindrical magnetic pole 201. These blocks generate a strong magnetic field gradient locally, disrupting the conditions for a stable beam trajectory and inducing rapid radial oscillations, or radial resonance, causing the beam trajectory to shift significantly outward within a few revolutions.

[0063] Graphite beam cutter 501: Located downstream of regenerator 507, it is used to physically cut and peel off the beam that has shifted outward due to resonance and guide it into the extraction channel.

[0064] The magnetic channel system is composed of multiple hollow channel units made of passive soft magnetic materials, such as electrical pure iron, connected end to end. Specifically, the hollow channel unit consists of magnetic channel one 502, magnetic channel two 503, magnetic channel three 504, and magnetic channel four 505. These four components are arranged end to end along the beam extraction direction, and they are located on the same mid-plane. It can also be simply understood that the center positions of these four components are on the same horizontal plane. Extending from the edge region of the cylindrical magnetic pole 201 and passing through the magnetic yoke 103, it forms a beam extraction channel that runs through the magnetic yoke. The function of this magnetic channel system is to shield the strong external superconducting magnetic field and provide a near-zero magnetic field channel for the extracted proton beam, so that it can get rid of the constraint of the main magnetic field and leave the main magnet region smoothly. The tapered design of the inner wall of each magnetic channel unit can produce a certain focusing effect on the beam.

[0065] Quadruple lens assembly 506: Located at the exit of the magnetic channel, it is used to focus and correct astigmatism of the extracted beam with a certain degree of divergence, so that its emittance matches the subsequent beam transmission line.

[0066] Harmonic extraction coil 508: Installed near the extraction path, it is supplied with a current of a specific frequency to generate a perturbation magnetic field, which is used to precisely fine-tune the beam extraction position.

[0067] VI. Vacuum System

[0068] The vacuum structure in this embodiment features a simplified design. The boundary of the vacuum chamber is formed by the inner cavity of the yoke 103 of the main magnet system and the cryogenic thermostat shell of the conduction-cooled superconducting magnet system. A large O-ring provides a static seal between the two. This eliminates the need for a separate, complex vacuum container for the internal space of the main magnet, i.e., the accelerator vacuum chamber. Vacuum pipes are connected to the upper and lower ends of the yoke 103 for mounting turbomolecular pumps, serving as the main pump, dry roughing pump, gate valve, and vacuum gauge. Through two-stage evacuation, the required high vacuum environment can be established and maintained inside the accelerator, typically superior to... Pa.

[0069] VII. Lifting System

[0070] like Figure 1 and Figure 2 As shown, the lifting system facilitates the installation and maintenance of the equipment. The system includes the accelerator main support assembly 101 and the hydraulic lifting assembly 102. The hydraulic lifting assembly 102 consists of three or more sets of servo hydraulic cylinders evenly distributed along the circumference. The cylinder body of each hydraulic cylinder, that is, the fixed end, is installed on the lower half of the magnetic yoke and the main support assembly 101, while the movable end of its piston rod is connected to the upper half of the magnetic yoke. When internal maintenance is required, such as replacing the ion source or repairing the high-frequency cavity components, the hydraulic station drives all the hydraulic cylinders to lift synchronously, raising the upper half of the magnet, which weighs tens of tons, including the upper half of the magnetic yoke, magnetic poles and corresponding superconducting coil system, and then smoothly raising it, thereby completely exposing the internal space of the accelerator.

[0071] VIII. System Workflow

[0072] Based on the above structure, the workflow of the accelerator system in this embodiment is as follows:

[0073] Step 1, Preparation Stage: Start the vacuum system to evacuate the accelerator to a high vacuum; start the multi-stage refrigerator to cool the superconducting coil to and stabilize it at the superconducting operating temperature of 4.2K through conduction cooling; excite the superconducting coil to establish a stable, high-intensity, weak focusing magnetic field, such as the central 7T, in the magnetic pole gap.

[0074] Step 2, Injection and Acceleration Stage: The servo motor drives the moving plate of the rotating capacitor 301 to rotate at a constant speed, causing the frequency of the high-frequency system to scan periodically from high to low. During this process, the tuner 302 makes real-time fine adjustments based on the feedback signal to ensure that the frequency accurately tracks the preset curve. When the frequency scans to the preset capture window, the control system triggers the cold cathode Penning ion source 404 to ignite, generating a pulsed proton beam. Under the combined action of the central region absorber 403 and the high-frequency electric field, the protons are injected and captured into the acceleration track. Since the high-frequency frequency is precisely synchronized with the cyclotron frequency of the protons, the protons are continuously accelerated in hundreds of cyclotrons, and the energy is gradually increased to the target value, such as 210 MeV.

[0075] Step 3, Extraction Stage: The high-energy proton beam moves to the edge of the magnetic pole and undergoes radial resonance under the magnetic field disturbance caused by the regenerator 507. The trajectory expands rapidly and is then cut into the extraction channel by the graphite beam cutter 501. The beam leaves the main magnetic field region under the shielding and guidance of the hollow channel unit (i.e., the hollow channel composed of magnetic channel one 502, magnetic channel two 503, magnetic channel three 504, and magnetic channel four 505). Finally, after being focused and shaped by the four-stage lens assembly 506, it enters the subsequent beam transmission system for use in treatment.

[0076] Step 4, Maintenance Operation: When maintenance is required, turn off all power, allow the low-temperature thermostat to warm to room temperature, release the vacuum, and then start the hydraulic lifting assembly 102 to lift the upper half of the magnet as a whole, so that all internal components can be easily inspected or replaced.

[0077] The above description is merely a preferred embodiment of the present invention; however, the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and its improved concepts, should be covered within the scope of protection of the present invention.

Claims

1. A conduction-cooled superconducting synchrotron accelerator system for proton therapy, characterized in that, It includes the main magnet system, the conductive cooling superconducting magnet system, the high-frequency system, the ion source system, the central region system, the extraction system, and the vacuum system; The main magnet system includes a yoke (103) and cylindrical magnetic poles (201) disposed within the yoke (103). The surface of the pole tip (202) of the cylindrical magnetic pole (201) has a modulation curve that descends radially to form a weakly focused magnetic field, and the field index n satisfies 0. <n<1; The conductive cooling type superconducting magnet system includes a strong magnetic field superconducting coil, which is coaxially arranged around the cylindrical magnetic pole (201) of the main magnet system to provide a background magnetic field for the accelerator. The high-frequency system includes a radio frequency cavity (303) and a rotating capacitor (301). The radio frequency cavity (303) is disposed in the gap of the cylindrical magnetic pole (201). The rotating capacitor (301) is electrically connected to the radio frequency cavity (303) and is used to periodically adjust the capacitance of the resonant circuit so that the frequency change of the high-frequency voltage is synchronized with the cyclotron frequency of the proton beam. The ion source system includes a cold cathode Penning ion source (404), which is located at the center of the accelerator; The central region system includes a suction electrode (403) disposed in the central region of the radio frequency cavity (303); The extraction system is located at the edge region of the cylindrical magnetic pole (201) and is used to extract the proton beam accelerated to the target energy. The vacuum system includes a vacuum pump and a vacuum pipe, the vacuum pipe being connected to the magnetic yoke (103), and the main magnet system forming a vacuum chamber inside.

2. The proton therapy conductive cooling type superconducting synchrotron accelerator system according to claim 1, characterized in that, The main magnet system also includes a magnetic field pad strip (203) and a magnetic field pad block (204), which are disposed on the surface of the cylindrical magnetic pole (201) for local adjustment of the magnetic field.

3. The proton therapy conductive cooling type superconducting synchrotron accelerator system according to claim 1, characterized in that, The conductive cooling superconducting magnet system also includes a multi-stage refrigerator, a cryostat, and a heat-conducting component; the strong magnetic field superconducting coil is disposed inside the cryostat; one end of the heat-conducting component is connected to the cold head of the refrigerator, and the other end passes through the cryostat and is connected to the support frame of the strong magnetic field superconducting coil.

4. The proton therapy conductive cooling type superconducting synchrotron accelerator system according to claim 1, characterized in that, The rotating capacitor (301) includes a fixed plate and a movable plate driven by a servo motor, and the capacitance is changed periodically by the rotation of the movable plate.

5. The proton therapy conductive cooling type superconducting synchrotron accelerator system according to claim 1 or 4, characterized in that, The pulse beam output timing of the ion source system is periodically locked with the frequency modulation of the rotating capacitor (301).

6. The proton therapy conductive cooling type superconducting synchrotron accelerator system according to claim 1, characterized in that, The extraction system includes a regenerator (507), a magnetic channel, and a quadruple lens assembly (506); the regenerator (507) is a ferromagnetic protrusion disposed on the edge of the cylindrical magnetic pole (201); the magnetic channel is composed of multiple hollow channel units made of passive soft magnetic material connected in sequence and embedded in the magnetic yoke (103); the quadruple lens assembly (506) is disposed at the outlet of the magnetic channel.

7. The proton therapy conductive cooling type superconducting synchrotron accelerator system according to claim 1, characterized in that, The vacuum chamber boundary of the vacuum system is formed by the inner cavity of the yoke (103) of the main magnet system and the cryogenic thermostat shell of the conductive cooling superconducting magnet system sealed by a sealing ring.

8. The proton therapy conductive cooling type superconducting synchrotron accelerator system according to claim 1, characterized in that, It also includes a lifting system, which includes a hydraulic lifting assembly (102), the fixed end of which is connected to the lower half-yoke and the main support assembly (101), and the movable end of which is connected to the upper half-yoke.

9. The proton therapy conductive cooling type superconducting synchrotron accelerator system according to claim 1, characterized in that, The central magnetic field strength generated by the high magnetic field superconducting coil is not less than 5T, and the accelerator system can extract a proton beam with an energy of not less than 210MeV.

10. The proton therapy conductive cooling superconducting synchrotron accelerator system according to claim 3, characterized in that, The heat-conducting component is a flexible cooling strip made of high-purity aluminum or oxygen-free copper; the strong magnetic field superconducting coil is made of NbTi or... Superconducting wire winding.

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