Compact shallow valley type main magnet for cyclotron

Abstract

This invention relates to the field of proton cyclotron accelerator technology and discloses a shallow valley-type main magnet for a compact cyclotron accelerator, comprising a magnetic yoke, a cover plate, a magnetic pole base, magnetic pole bodies, and inserts assembled sequentially. The magnetic yoke adopts a horizontal square structure. In this invention, the magnetic yoke adopts a horizontal square structure, and the dovetail groove design of the bottom positioning block enables rapid and accurate positioning of the equipment without the need for additional pit excavation, significantly reducing the difficulty of pre-installation construction and site modification costs. Combined with the shallow valley design of the magnetic pole base, which reduces the valley depth and raises the valley magnetic field, the average magnetic field strength of the main magnet is significantly improved while ensuring the magnetic field gradient required for isochronous particle acceleration. With the compact circumferential distribution of eight separate fan-shaped magnetic pole bodies, the overall size of the equipment is effectively reduced, successfully adapting to scenarios with strict space constraints, such as medical radionuclide production and small-scale scientific research experiments.

Description

Technical Field

[0001] This invention relates to the field of proton cyclotron technology, specifically to a shallow valley main magnet for a compact cyclotron. Background Technology

[0002] A cyclotron is a device that confines particles to a magnetic field, causing them to cyclone within the magnet, and then accelerates them using a high-frequency electric field. A compact negative hydrogen cyclotron system consists of core components such as a cold cathode Penning ion source, a main magnet, a high-frequency cavity, an extraction system, a vacuum chamber, and a target chamber. Negative hydrogen is generated by the Penning source, extracted and accelerated by a high-voltage electrode, and undergoes near-circular motion under the confinement of an isochronous magnetic field. Continuous acceleration is achieved through high-frequency acceleration gaps, each acceleration increasing the particle's energy and radius. Finally, through stripping extraction, the negative hydrogen particles lose two electrons, deviating from their original trajectory under the influence of the magnetic field and striking the target.

[0003] Among them, the magnetic field generated by the main magnet is the key to continuously accelerating particles and ensuring that they do not deviate significantly from the high-frequency phase when passing through the acceleration gap. The main magnet is also crucial to ensuring that the acceleration current of the negative hydrogen ion beam (above 100uA) in the compact isochronous cyclotron accelerator system reaches 10MeV. However, the shallow valley-type main magnet of the compact isochronous horizontal cyclotron accelerator still faces the following challenges: the current cyclotron accelerator is large in size and expensive. How to reduce the size and cost while ensuring performance, so as to broaden its application fields and adapt to more scenarios, has become a major challenge in design. Traditional vertical cyclotron accelerators rely on hydraulic lifting devices to symmetrically open the magnets, which not only increases the difficulty of accelerator installation and commissioning, but also makes the operation and maintenance process more complicated. To address this, we propose a shallow valley-type main magnet for compact cyclotron accelerators. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a shallow valley-type main magnet for a compact cyclotron, solving the problem that current cyclotrons are large in size and expensive. How to reduce size and cost while ensuring performance, so as to broaden their application fields and adapt to more scenarios, has become a major design challenge. Traditional vertical cyclotrons rely on hydraulic lifting devices to symmetrically open the magnets, which not only increases the difficulty of accelerator installation and commissioning, but also makes the operation and maintenance process more complicated.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a shallow-valley main magnet for a compact cyclotron accelerator, comprising a yoke, a cover plate, a pole base, a pole body, and an insert assembled sequentially. The yoke adopts a horizontal square structure, with a positioning block with a dovetail groove at its bottom for rapid and precise positioning. The cover plate is fixed to the surface of the yoke and has openings for a high-frequency cavity inner rod, a vacuum opening, a coil fixing device opening, and a pole fixing opening. The pole base is embedded inside the yoke and locked through the pole fixing opening. The pole body is embedded in the groove of the pole base. The insert has a bilaterally symmetrical irregular curved structure. The device is detachably mounted between the magnetic pole body and the magnetic pole base. The magnetic yoke adopts a horizontal square structure, and the dovetail groove design of the bottom positioning block enables the device to be quickly and accurately positioned without the need for additional pit excavation, which greatly reduces the difficulty of early construction and site modification costs. Combined with the shallow valley design of the magnetic pole base, which reduces the depth of the valley area and raises the magnetic field of the valley area, the average magnetic field strength of the main magnet is significantly improved while ensuring the magnetic field gradient required for isochronous acceleration of particles. With the compact circumferential distribution of 8 separate fan-shaped magnetic pole bodies, the overall size of the device is effectively reduced, making it suitable for scenarios with strict space restrictions, such as medical radionuclide production and small-scale scientific research experiments.

[0006] Preferably, the central axes of the cover plate, the magnetic pole base, and the magnetic pole body are strictly collinear. The magnetic pole body has a separated fan-shaped structure, and its magnetic pole angle increases radially. The magnetic field isochronous and stable through a triple collaborative design: First, the magnetic pole base is made of DT4 magnetic material, which has excellent magnetic permeability and lays the foundation for magnetic field uniformity. Second, the eight separated fan-shaped magnetic pole bodies are symmetrically distributed with the three centers collinear as the center, and the magnetic pole angle gradually increases, which accurately matches the radially increasing magnetic field required for the isochronous acceleration of particles, reduces the interference of magnetic field harmonic components on the beam, reduces beam loss, and ensures that the particle extraction current intensity reaches more than 100μA. Third, the side-detachable double-sided symmetrical irregular curve strips can quickly correct the magnetic field deviation caused by processing and assembly errors through cutting or padding, without the need for secondary processing of the complex magnetic pole body, which greatly improves the magnetic field padding efficiency and ensures that particles are stably accelerated to the target energy of 10MeV.

[0007] Preferably, the main magnet body formed by the yoke and the cover plate adopts a direct symmetrical opening structure, eliminating the need for a hydraulic lifting device. The main magnet as a whole adopts a direct symmetrical opening design, replacing the hydraulic lifting device relied upon by traditional vertical cyclotrons, significantly shortening the equipment opening time, simplifying the installation and commissioning process, and reducing the maintenance cost and failure risk of the hydraulic system. The cover plate integrates the high-frequency cavity inner rod opening, vacuum opening, coil fixing device opening, and magnetic pole fixing opening, with a high degree of functional integration. Combined with the modular structure design, it further reduces the overall cost of equipment manufacturing, transportation, and long-term operation and maintenance, meeting the application requirements of high efficiency and low consumption in industrial equipment.

[0008] Preferably, the magnetic pole base is integrally formed using DT magnetic conductive material, and is rigidly connected to the magnetic yoke through the magnetic pole fixing opening. The triple sealing design, consisting of the magnetic pole base pressing against the vacuum chamber, the vacuum opening connecting to the pumping assembly, and the sealing groove on the inner wall of the high-frequency chamber rod opening fitted with a sealing ring, constructs a stable and reliable high vacuum environment, reduces collision losses between particles and air molecules, and provides the necessary conditions for the acceleration of negative hydrogen ions. This design enables the equipment to adapt to scenarios with stringent requirements for environmental cleanliness and vacuum stability, such as medical radionuclide production, and significantly improves the operational reliability and environmental adaptability of the device.

[0009] Preferably, the inlay is used to correct magnetic field errors. By cutting or padding the irregular curve of the inlay, the magnetic field meets the isochronism requirement.

[0010] Preferably, there are a total of eight magnetic poles, which are divided into two groups and evenly distributed in a circle with the central axis as the center. The two groups of magnetic poles are arranged symmetrically.

[0011] Preferably, the opening in the coil fixing device is used to install the coil fixing structure, the opening in the high-frequency cavity inner rod is used to insert the high-frequency cavity inner rod, and the vacuum opening is used to connect the vacuum pumping assembly.

[0012] Preferably, the opening in the coil fixing device is used to install the coil fixing structure, the opening in the high-frequency cavity inner rod is used to insert the high-frequency cavity inner rod, and the vacuum opening is used to connect the vacuum pumping assembly.

[0013] Preferably, the high-frequency cavity inner rod opening and the vacuum opening are symmetrically distributed on both sides of the center of the cover plate, and the inner wall of the high-frequency cavity inner rod opening is provided with a sealing groove, and a sealing ring is adapted to be installed in the sealing groove to achieve a sealed connection.

[0014] In summary, the technical effects and advantages of this invention are as follows:

[0015] 1. In this invention, the magnetic yoke adopts a horizontal square structure, and the dovetail groove design of the bottom positioning block enables the equipment to be positioned quickly and accurately without the need for additional pit excavation, which greatly reduces the difficulty of early construction and site modification costs. Combined with the shallow valley design of the magnetic pole base to reduce the valley depth and raise the valley magnetic field, the average magnetic field strength of the main magnet is significantly improved while ensuring the magnetic field gradient required for the isochronous acceleration of particles. With the compact circumferential distribution of 8 separate fan-shaped magnetic poles, the overall size of the equipment is effectively reduced, and it is successfully adapted to scenarios with strict space restrictions, such as medical radionuclide production and small-scale scientific research experiments.

[0016] 2. In this invention, the isochronism and stability of the magnetic field are ensured through a triple synergistic design: First, the magnetic pole base is made of DT4 magnetic material, which has excellent magnetic permeability and lays the foundation for magnetic field uniformity; Second, the eight separate sector-shaped magnetic poles are symmetrically distributed with three collinear centers as the center, and the magnetic pole angle gradually increases, accurately matching the radially increasing magnetic field required for isochronous acceleration of particles, reducing the interference of magnetic field harmonic components on the beam, reducing beam loss, and ensuring that the particle extraction current intensity reaches more than 100μA; Third, the detachable double-sided symmetrical irregular curve inlay can quickly correct the magnetic field deviation caused by processing and assembly errors through cutting or padding, without the need for secondary processing of the complex magnetic pole body, greatly improving the magnetic field padding efficiency and ensuring that particles are stably accelerated to the target energy of 10MeV.

[0017] 3. In this invention, the main magnet adopts a direct symmetrical opening design, replacing the hydraulic lifting device relied upon by traditional vertical cyclotrons, which significantly shortens the equipment opening time, simplifies the installation and commissioning process, and reduces the maintenance cost and failure risk of the hydraulic system. The cover plate integrates the high-frequency cavity inner rod opening, vacuum opening, coil fixing device opening and magnetic pole fixing opening, with high functional integration. Combined with the modular structure design, it further reduces the overall cost of equipment manufacturing, transportation and long-term operation and maintenance, meeting the application requirements of high efficiency and low consumption of industrial equipment.

[0018] 4. In this invention, a triple sealing design is used to construct a stable and reliable high vacuum environment by using a magnetic pole base to press the vacuum chamber, a vacuum opening to connect the pumping assembly, and a sealing groove on the inner wall of the high-frequency chamber rod opening to install a sealing ring. This reduces the collision loss between particles and air molecules and provides the necessary conditions for the acceleration of negative hydrogen ions. This design enables the equipment to adapt to scenarios with stringent requirements for environmental cleanliness and vacuum stability, such as the production of medical radionuclides, and greatly improves the operational reliability and environmental adaptability of the device. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of a shallow valley main magnet for a compact cyclotron accelerator according to the present invention.

[0020] Figure 2 This is a rear view structural schematic diagram of a shallow valley-type main magnet for a compact cyclotron accelerator according to the present invention.

[0021] Figure 3 This is an exploded structural diagram of a shallow valley-type main magnet for a compact cyclotron accelerator according to the present invention.

[0022] Figure 4 This is a schematic diagram of the connection between the magnetic pole base and the cover plate in a shallow valley-type main magnet for a compact cyclotron according to the present invention.

[0023] Figure 5This is a schematic diagram of the insert structure in a shallow valley-type main magnet for a compact cyclotron according to the present invention.

[0024] In the diagram: 1. Magnetic yoke; 2. Cover plate; 3. Magnetic pole base; 4. Magnetic pole body; 5. Inlay strip; 6. Opening for the inner rod of the high-frequency cavity; 7. Vacuum opening; 8. Opening for the coil fixing device; 9. Opening for the magnetic pole fixing. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] The principle of isochronous cyclotron accelerators is that the cyclotron frequency of particles remains constant; its isochronous principle is stated as follows: ;

[0027] In the formula, Let be the average field at any radius; Let be the magnetic induction intensity corresponding to the rest mass of the particle; r be the cyclotron radius of the particle; f be the cyclotron frequency of the particle; and c be the speed of light. According to the isochronism principle of cyclotrons, once the radius is determined, the average magnetic field corresponding to that radius is also determined.

[0028] Based on the above principles, refer to Figures 1-5 The diagram shows a shallow-valve main magnet for a compact cyclotron, comprising a yoke 1, a cover plate 2, a pole base 3, a pole body 4, and an insert 5, assembled sequentially. The yoke 1 has a horizontal square structure with a positioning block with a dovetail groove at its bottom for rapid and precise positioning. The cover plate 2 is fixed to the surface of the yoke 1 and has openings for a high-frequency cavity rod 6, a vacuum opening 7, a coil fixing device opening 8, and a pole fixing opening 9. The pole base 3 is embedded inside the yoke 1 and locked in place by the pole fixing opening 9. The pole body 4 is embedded in the groove 49 of the pole base 3. The insert 5 has a bilaterally symmetrical irregular curved structure and is detachable from the side. Positioned between the magnetic pole body 4 and the magnetic pole base 3, the magnetic yoke 1 adopts a horizontal square structure. The dovetail groove design of the bottom positioning block enables the equipment to be quickly and accurately positioned without the need for additional pit excavation, which greatly reduces the difficulty of early construction and site modification costs. Combined with the shallow valley design of the magnetic pole base 3, which reduces the valley depth and raises the valley magnetic field, the average magnetic field strength of the main magnet is significantly improved while ensuring the magnetic field gradient required for isochronous acceleration of particles. With the compact circumferential distribution of 8 separate fan-shaped magnetic pole bodies 4, the overall size of the equipment is effectively reduced, making it suitable for scenarios with strict space restrictions, such as medical radionuclide production and small-scale scientific research experiments.

[0029] Preferably, the central axes of the cover plate 2, the magnetic pole base 3, and the magnetic pole body 4 are strictly collinear. The magnetic pole body 4 has a separated fan-shaped structure, and its magnetic pole angle increases radially. The magnetic field isochronous and stable through a triple collaborative design: First, the magnetic pole base 3 is made of DT4 magnetic material, which has excellent magnetic permeability and lays the foundation for magnetic field uniformity. Second, the eight separated fan-shaped magnetic pole bodies 4 are symmetrically distributed with the three centers collinear as the center, and the magnetic pole angle gradually increases, which accurately matches the radially increasing magnetic field required for the isochronous acceleration of particles, reduces the interference of magnetic field harmonic components on the beam, reduces beam loss, and ensures that the particle extraction current intensity reaches more than 100μA. Third, the side-detachable double-sided symmetrical irregular curve inlay 5 can quickly correct the magnetic field deviation caused by processing and assembly errors through cutting or padding, without the need for secondary processing of the complex magnetic pole body 4, which greatly improves the magnetic field padding efficiency and ensures that particles are stably accelerated to the target energy of 10MeV.

[0030] Preferably, the main magnet body, consisting of the yoke 1 and the cover plate 2, adopts a direct symmetrical opening structure, eliminating the need for a hydraulic lifting device. The main magnet as a whole adopts a direct symmetrical opening design, replacing the hydraulic lifting device relied upon by traditional vertical cyclotrons, significantly shortening the equipment opening time, simplifying the installation and commissioning process, and reducing the maintenance costs and failure risks of the hydraulic system. The cover plate 2 integrates the high-frequency cavity inner rod opening 6, vacuum opening 7, coil fixing device opening 8, and magnetic pole fixing opening 9, achieving a high degree of functional integration. Combined with the modular structure design, this further reduces the overall cost of equipment manufacturing, transportation, and long-term operation and maintenance, meeting the application requirements of high efficiency and low consumption in industrial equipment.

[0031] Preferably, the magnetic pole base 3 is integrally formed using DT magnetic conductive material. It forms a rigid connection with the magnetic yoke 1 through the magnetic pole fixing opening 9. The triple sealing design, which involves the magnetic pole base 3 pressing against the vacuum chamber, the vacuum opening 7 connecting to the pumping assembly, and the sealing groove on the inner wall of the high-frequency chamber rod opening 6 fitted with a sealing ring, constructs a stable and reliable high vacuum environment, reduces collision losses between particles and air molecules, and provides the necessary conditions for the acceleration of negative hydrogen ions. This design enables the equipment to adapt to scenarios with stringent requirements for environmental cleanliness and vacuum stability, such as the production of medical radionuclides, and significantly improves the operational reliability and environmental adaptability of the device.

[0032] Preferably, the inlay 5 is used to correct magnetic field errors. By cutting or padding the irregular curve of the inlay 5, the magnetic field can meet the isochronous requirements.

[0033] Preferably, there are a total of eight magnetic poles 4, which are divided into two groups and evenly distributed in a circle with the central axis as the center. The two groups of magnetic poles 4 are arranged symmetrically.

[0034] Preferably, the coil fixing device opening 8 is used to install the coil fixing structure, the high-frequency cavity inner rod opening 6 is used to pass through the high-frequency cavity inner rod, and the vacuum opening 7 is used to connect the vacuum pumping assembly.

[0035] Preferably, the coil fixing device opening 8 is used to install the coil fixing structure, the high-frequency cavity inner rod opening 6 is used to pass through the high-frequency cavity inner rod, and the vacuum opening 7 is used to connect the vacuum pumping assembly.

[0036] Preferably, the high-frequency cavity inner rod opening 6 and the vacuum opening 7 are symmetrically distributed on both sides of the center of the cover plate 2. The inner wall of the high-frequency cavity inner rod opening 6 is provided with a sealing groove, and a sealing ring is fitted into the sealing groove to achieve a sealed connection.

[0037] In the embodiments of this invention, the design parameters of the shallow valley-shaped main magnet of the compact isochronous horizontal cyclotron are shown in the table below:

[0038] In the embodiments of this invention, by combining a compact magnet design, the volume and space occupied by the magnet are successfully reduced, the opening method of the main magnet is optimized, and the system is simplified, thereby improving the installation and debugging efficiency of the accelerator. At the same time, the magnet padding efficiency is improved, the drilling operation is minimized, and the vacuum cavity is pressed by the magnetic pole base 3, avoiding damage to the vacuum system and effectively enhancing the operational stability of the accelerator.

[0039] Working principle of the invention: During the main magnet installation stage, the magnetic yoke 1 adopts a horizontal square design. The dovetail groove of the bottom positioning block can quickly complete the equipment positioning without the need for additional pit construction. At the same time, the magnetic pole base 3 is embedded and fixed in the magnetic yoke 1 through the magnetic pole fixing opening 9 to ensure structural stability. When installing the vacuum system, the vacuum chamber is first placed under the magnetic pole base 3, and then the vacuum chamber is pressed by the fixing of the magnetic pole base 3 and the magnetic yoke 1. With the vacuum pumping component connected to the vacuum opening 7 on the cover plate 2, and the sealing ring of the sealing groove of the inner wall of the high frequency cavity rod opening 6, vacuum leakage can be effectively reduced, providing a high vacuum environment for particle acceleration.

[0040] In terms of magnetic field generation and isochronous control, the magnetic pole angle of the eight separate fan-shaped magnetic pole bodies 4 increases with the radius, which can match the "magnetic field increasing along the radius" required for the isochronous acceleration of particles. The magnetic pole base 3 significantly improves the average magnetic field strength of the main magnet by reducing the valley depth and raising the valley magnetic field. This not only meets the magnetic field requirements for particle acceleration but also greatly reduces the overall volume of the main magnet. When there is a deviation between the actual magnetic field and the calculated isochronous field due to processing and assembly errors, it can be corrected by the strip 5 that is detachably installed between the magnetic pole body 4 and the magnetic pole base 3 on the side. The irregular curves of the symmetrically distributed strip 5 can be cut or padded to adjust the local magnetic field without processing the entire magnetic pole body 4. This efficiently ensures the isochronous nature of the magnetic field and ensures that the particles are continuously accelerated to the target energy of 10MeV.

[0041] During accelerator operation and maintenance, the main magnet, consisting of the yoke 1 and the cover plate 2, adopts a direct symmetrical opening design. Compared with traditional hydraulic lifting devices, this allows for quick equipment opening and simplifies the installation and debugging process. The coil fixing device opening 8 is used to install the coil fixing structure, providing stable support for the coil that generates the magnetic field. The high-frequency cavity inner rod opening 6 allows the high-frequency cavity inner rod to pass through, ensuring the synergistic effect of the high-frequency electric field and magnetic field. This achieves an increase in energy for each particle passing through the acceleration gap. At the same time, the symmetrical design of the magnetic field reduces magnetic field harmonic components, lowers beam loss, and ensures that the particle extraction current reaches more than 100 μA, ultimately meeting the needs of accelerating negative hydrogen ions and producing radioactive nuclides.

[0042] All electrical components mentioned in this article are connected to an external main controller and 220V AC mains power, and the main controller can be a conventional known device such as a computer that can control it.

[0043] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A shallow valley main magnet for a compact cyclotron, characterized by: The assembly includes a magnetic yoke (1), a cover plate (2), a magnetic pole base (3), a magnetic pole body (4), and an inlay (5) assembled in sequence. The magnetic yoke (1) adopts a horizontal square structure and has a positioning block with a dovetail groove at its bottom to achieve rapid and accurate positioning. The cover plate (2) is fixed to the surface of the magnetic yoke (1) and has a high-frequency cavity internal rod opening (6), a vacuum opening (7), a coil fixing device opening (8), and a magnetic pole fixing opening (9). The magnetic pole base (3) is embedded inside the magnetic yoke (1) and locked through the magnetic pole fixing opening (9). The magnetic pole body (4) is embedded in the groove of the magnetic pole base (3). The inlay (5) is a double-sided symmetrical irregular curve structure and is assembled between the magnetic pole body (4) and the magnetic pole base (3) in a side-detachable manner.

2. A shallow valley main magnet for a compact cyclotron according to claim 1, characterized in that: The central axes of the cover plate (2), the magnetic pole base (3) and the magnetic pole body (4) are strictly collinear. The magnetic pole body (4) has a separate fan-shaped structure, and its magnetic pole angle is set to increase along the radial direction.

3. A shallow valley main magnet for a compact cyclotron according to claim 1, characterized in that: The main magnet body formed by the yoke (1) and the cover plate (2) adopts a direct symmetrical opening structure, which does not require the assistance of a hydraulic lifting device.

4. A shallow valley main magnet for a compact cyclotron according to claim 1, characterized in that: The magnetic pole base (3) is integrally formed using DT4 magnetic conductive material and is rigidly connected to the magnetic yoke (1) through the magnetic pole fixing opening (9).

5. The shallow valley main magnet for a compact cyclotron according to claim 1, characterized in that: The inlay (5) is used to correct magnetic field errors. By cutting or padding the irregular curve of the inlay (5), the magnetic field meets the isochronous requirements.

6. A shallow valley main magnet for a compact cyclotron according to claim 1, characterized in that: There are a total of eight magnetic poles (4), which are divided into two groups and evenly distributed around the central axis. The two groups of magnetic poles (4) are arranged symmetrically.

7. A shallow valley main magnet for a compact cyclotron according to claim 1, characterized in that: The opening (8) of the coil fixing device is used to install the coil fixing structure, the opening (6) of the high-frequency cavity inner rod is used to pass through the high-frequency cavity inner rod, and the vacuum opening (7) is used to connect the vacuum pumping assembly.

8. A shallow valley main magnet for a compact cyclotron according to claim 1, characterized in that: The opening (8) of the coil fixing device is used to install the coil fixing structure, the opening (6) of the high-frequency cavity inner rod is used to pass through the high-frequency cavity inner rod, and the vacuum opening (7) is used to connect the vacuum pumping assembly.

9. A shallow valley main magnet for a compact cyclotron according to claim 1, characterized in that: The high-frequency cavity inner rod opening (6) and the vacuum opening (7) are symmetrically distributed on both sides of the center of the cover plate (2). The inner wall of the high-frequency cavity inner rod opening (6) is provided with a sealing groove, and a sealing ring is fitted in the sealing groove to achieve a sealed connection.

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