A desktop cyclotron high-frequency cavity frequency tuning mechanism

Abstract

The application discloses a frequency tuning mechanism of a desktop cyclotron high-frequency cavity, comprising a high-frequency cavity D-plate analog piece arranged along a horizontal direction, a tuning capacitor plate, a main vacuum chamber analog piece, a vacuum sealing corrugated pipe assembly welding piece, a linear stepping motor containing a screw rod, an anti-rotation limiting strip and an anti-rotation limiting side plate; the vacuum sealing corrugated pipe assembly welding piece is provided with a connecting inner core which is along an axial direction, one end of the connecting inner core extends into the vacuum sealing corrugated pipe assembly welding piece and the other end extends into the main vacuum chamber analog piece; two inner thread holes are arranged in the connecting inner core, the inner thread holes are not drilled through, one inner thread hole is matched with an outer thread of one end of the screw rod of the linear stepping motor, and the other inner thread hole is matched with an outer thread of the tuning capacitor plate; the application adopts a return type corrugated pipe structure, so that the combined structure is compact and occupies a small space, and the small size of the desktop cyclotron can be satisfied, and the application is also applicable to other small low-power cyclotrons.

Description

Technical Field

[0001] This invention relates to a high-frequency cavity frequency tuning mechanism for a particle accelerator, specifically a high-frequency cavity frequency tuning mechanism for a desktop cyclotron accelerator, belonging to the field of particle accelerator technology. Background Technology

[0002] Isochronous cyclotron accelerators typically have a fixed operating frequency for their particle accelerating voltage, and the high-frequency cavity resonates at this frequency for optimal performance. During the installation and commissioning phase of the high-frequency cavity, the intrinsic resonant frequency is adjusted to the required operating frequency by means of local machining of the cavity. However, during accelerator operation, thermal and mechanical deformation after power is fed into the cavity can cause the resonant frequency to drift, resulting in poor cavity resonance, increased power loss, and decreased operational stability. Therefore, a high-frequency cavity tuning mechanism is needed to continuously track and compensate for changes in the cavity resonant frequency, ensuring that the resonant frequency remains constant.

[0003] High-frequency cavity frequency tuning mechanisms typically change the cavity resonant frequency by altering the local distributed capacitance around the cavity's D-plate. This is achieved by changing the distance between the tuning capacitor plate and the D-plate, thereby altering the capacitance between them and causing a change in the cavity resonant frequency. This compensates for changes in the cavity's intrinsic resonant frequency caused by factors such as thermal deformation, ensuring that the cavity's intrinsic resonant frequency remains constant.

[0004] One of the design challenges of high-frequency cavity frequency tuning mechanisms is: Figure 14As shown, this relates to the grounding issue of the tuning capacitor plate. High-frequency cavities operate in a vacuum environment, requiring the tuning capacitor plate to be properly grounded at high frequencies. This grounding is typically achieved by connecting it to the accelerator's main vacuum chamber or the cavity's outer shell. In existing high-frequency cavity frequency tuning mechanisms, the tuning capacitor plate is generally mounted on a movable rod within a vacuum. This rod is led out of the vacuum via a bellows, and its translation is achieved through an electric translation mechanism outside the vacuum, thus enabling the tuning capacitor plate to translate within the vacuum. There are two grounding methods for the tuning capacitor plate: one is to achieve a dynamic electrical connection between the movable rod and its external ground potential component (such as the main vacuum chamber) using beryllium copper finger-shaped springs; the other is to connect the back of the tuning capacitor plate or the movable rod to its external ground potential component using copper foil, with the copper foil bent into an appropriate shape to compensate for changes in the dynamic connection distance. Both existing grounding methods for tuning capacitor boards suffer from mechanical wear: The first method, using beryllium copper finger springs to achieve dynamic electrical connection between the movable rod and external grounding components such as the main vacuum chamber, suffers from material wear at the contact points due to long-term friction. This wear eventually leads to failure and arcing at the contact point. The second method, connecting the back of the tuning capacitor board to its external grounding component using copper foil, is prone to breakage due to repeated bending at the copper foil's curved sections. These two issues necessitate the use of bellows for high-frequency grounding, but the O-rings at the flanges at both ends of the bellows are susceptible to arcing and burning.

[0005] The second challenge in designing a high-frequency cavity frequency tuning mechanism: Figure 15 As shown, the existing linear drive mechanism is located at the rear end of the bellows, occupying a large space. The existing linear drive mechanism generally includes a motor, reducer, coupling, thrust bearing and its back-tightening nut, motor mounting bracket, trapezoidal lead screw and trapezoidal nut, linear guide rail, support mounting base, limit switch, and mechanical limit structures at both ends of the stroke, resulting in a large overall size for the high-frequency cavity frequency tuning mechanism, which cannot meet the requirements of an ultra-small desktop cyclotron high-frequency cavity frequency tuning mechanism.

[0006] The third challenge in designing a high-frequency cavity frequency tuning mechanism is: Figure 15As shown, existing technology involves installing a replaceable adjustment pad of a certain thickness between the tuning capacitor plate and the movable rod. This ensures that when the tuning capacitor plate is positioned at an appropriate midpoint of the frequency tuning mechanism's travel, the cavity resonant frequency is the high-frequency required for accelerator operation. This allows for appropriate adjustment of the cavity frequency in both directions during equipment operation. However, this requires multiple adjustment pads of different thicknesses. Furthermore, subsequent equipment maintenance or component replacement causing changes in the cavity resonant frequency necessitates pad replacement to ensure the tuning capacitor plate is positioned at the appropriate midpoint during cavity resonance. The method for replacing the adjustment pad involves drilling holes in the center of both the tuning capacitor plate and the adjustment pad, and providing threaded holes at the end of the movable rod. Screws are used to fix the tuning capacitor plate and adjustment pad to the end of the movable rod. Replacing adjustment pads of different thicknesses sometimes requires replacing screws of different lengths. This structure also makes vacuum evacuation difficult in the enclosed space of the threaded bottom hole, reducing the local vacuum level in this area. Since this area is a high-voltage radio frequency region, a low vacuum level may cause localized arcing or even electron multiplication effects, leading to equipment instability.

[0007] In summary, the design challenges of high-frequency cavity frequency tuning mechanisms are: large equipment size, unreliable grounding of the tuning capacitor board, the need to prepare and replace adjustment pads and screws to adjust the position of the tuning capacitor board properly, which may cause local arcing or even electron multiplication effect when the vacuum level is low, resulting in unstable equipment operation. Summary of the Invention

[0008] This invention addresses the problems existing in the prior art by proposing a desktop cyclotron high-frequency cavity frequency tuning mechanism. The purpose is to solve the problems that the prior art cannot solve, such as the large size of the equipment, unreliable grounding of the tuning capacitor plate, the need to prepare and replace adjustment pads and screws to adjust the position of the tuning capacitor plate properly, and the possibility of local arcing or even electron multiplication effect when the vacuum level is low, which may cause the equipment to be unstable.

[0009] To solve its technical problems, the present invention proposes the following technical solutions:

[0010] A desktop cyclotron high-frequency cavity frequency tuning mechanism includes: a high-frequency cavity D-plate simulator 5, a tuning capacitor plate 2, a main vacuum chamber simulator 6, a vacuum-sealed bellows assembly 1, a linear stepper motor 7 with a lead screw, an anti-rotation limiting strip 3, and an anti-rotation limiting side plate 4, arranged horizontally from right to left or from left to right; the main vacuum chamber simulator 6, the vacuum-sealed bellows assembly 1, the linear stepper motor 7, the anti-rotation limiting strip 3, and the anti-rotation limiting side plate 4 are combined with an O-ring seal 8, an elastic wire mesh 9, a micro switch 10, an A screw 11, a B screw 12, an A washer 13, a C screw 14, a B washer 15, a D screw 16, an E screw 17, and a C washer 18 to drive the tuning capacitor plate 2 to move axially, thereby adjusting the surface distance between the tuning capacitor plate 2 and the high-frequency cavity D-plate simulator 5, and adjusting the surface distance to adjust the high-frequency cavity frequency;

[0011] Its characteristics are:

[0012] The vacuum-sealed bellows assembly 1 is provided with a connecting inner core 104. One end of the connecting inner core 104 extends into the vacuum-sealed bellows assembly 1 along the axial direction, and the other end extends into the main vacuum chamber simulation component 6. The connecting inner core 104 is provided with two internal threaded holes. The two internal threaded holes are not drilled through. One internal threaded hole is engaged with the external thread of the linear stepper motor 7 lead screw, and the other internal threaded hole is engaged with the external thread of the tuning capacitor plate 2.

[0013] The linear stepper motor 7 is a hollow motor with a nut at the center of its rotor. A lead screw is screwed into the center of the nut. The lead screw is located inside the bellows and is directly fixed to the connecting inner core 104. The rotation of the motor rotor drives the nut to rotate. The external thread at the left end of the lead screw has the same specification as the internal thread at the right end of the connecting inner core 104. A part of the left end of the lead screw is screwed into the connecting inner core 104 to achieve the connection between the two.

[0014] The right end of the tuning capacitor plate 2 is provided with an external thread, which is fixed to the connecting inner core 104 by the threaded connection. The two surfaces are tightly and well bonded, realizing high-frequency electrical connection without mechanical movement loss, which is conducive to the long-term stable operation of the equipment.

[0015] The vacuum-sealed bellows assembly 1 includes: a vacuum-sealed grounding cylinder 101, a transition flange 102, a welded bellows 103, and a connecting inner core 104. The four parts are welded together to form the vacuum-sealed bellows assembly 1, and the four parts form a good high-frequency electrical connection at their ends.

[0016] The elastic wire mesh 9 is made of beryllium copper, which has good elasticity and conductivity. It is installed in the inner groove of the vacuum-sealed grounding cylinder 101. The beryllium copper wire mesh enables a good high-frequency electrical connection between the vacuum-sealed corrugated pipe assembly 1 and the main vacuum chamber simulation component 5.

[0017] The depth to which the lead screw of the linear stepper motor 7 is screwed into the connecting inner core is adjustable, and the distance T between the right end face of the connecting inner core 104 and the threaded step surface of the lead screw is variable: by setting and adjusting an appropriate distance T, the tuning capacitor plate can be positioned at an appropriate position in the middle of the effective stroke of the tuning mechanism when the cavity resonates.

[0018] Furthermore, the transition flange 102 of the vacuum-sealed bellows assembly 1 has four threaded holes on its end face for connecting and fixing the linear stepper motor 7; two threaded holes are provided on each of the two sides for connecting and fixing two anti-rotation limiting side plates 4; the welded bellows 103 has good axial elastic deformation capability and can achieve large axial elastic deformation while maintaining vacuum sealing.

[0019] Furthermore, the left flange end face of the vacuum-sealed grounding cylinder 101 is provided with two grooves, and the inner groove is filled with an elastic wire mesh 9. The elastic wire mesh 9 is located inside the O-ring seal, which prevents the high-frequency electric field from passing through the O-ring seal position and causing arcing and damage to the O-ring seal, thereby effectively protecting the vacuum seal.

[0020] Furthermore, the linear stepper motor 7 is directly installed in the threaded hole on the end face of the transition flange 102; a local distributed capacitance of the cavity is formed between the opposite surfaces of the tuning capacitor plate 2 and the high-frequency cavity D plate simulation component 5, and the value of the local distributed capacitance is changed by changing the distance L between the two surfaces, thereby changing the resonant frequency of the cavity.

[0021] Furthermore, there are two anti-rotation limiting side plates 4, one end of which has two through holes and the other end has a rectangular groove structure inside; they are fixed to both sides of the transition flange 102 by E screws 17 and C washers 18; the anti-rotation limiting strip 3 is long and has a through hole in the middle, and the end concentric with the through hole has a racetrack-shaped stepped recessed structure in the middle; the two ends of the anti-rotation limiting strip 3 are inserted into the long groove of the two anti-rotation limiting side plates 4, and at this time the range of motion of the anti-rotation limiting strip 3 in the long groove corresponds exactly to the required range of motion of the tuning capacitor plate.

[0022] Furthermore, the lead screw of the linear stepper motor 7 has a symmetrical planar structure at its end. The anti-rotation limiting strip 3 is connected and fixed to the right end of the lead screw by screw A 11. The recessed part of the connecting and fixing strip 3 is exactly aligned with... Figure 11 The right end of the lead screw is removed to accommodate the change; the front and rear ends of the anti-rotation limit strip 3 are inserted into the long slots of the two anti-rotation limit side plates 4; the linear stepper motor 7 is fixed to the transition flange 102 by C screws 14 and B washers 15.

[0023] Furthermore, by combining the right-end structure of the linear stepper motor 7 lead screw, the anti-rotation limiting strip 3, the long slot structure of the anti-rotation limiting side plate 4, and the micro switch 10, a combination of lead screw anti-rotation and translation limiting structure is achieved: the right end of the lead screw has an internal thread and a symmetrical planar structure at the end. The anti-rotation limiting strip 3 is connected and fixed to the right end of the lead screw by screw A 14. The concave part of the anti-rotation limiting strip 3 is exactly adapted to the planar structure formed by removing the part of the right end of the lead screw, and the two cannot rotate relative to each other. This allows the two ends of the anti-rotation limiting strip 3 to be inserted into the long slots of the two anti-rotation limiting side plates 4. When the equipment is running, the anti-rotation limiting strip 3 cannot achieve angular positioning. The anti-rotation limit bar 3 is inserted into the long slots of the two anti-rotation limit side plates at both ends, thus restricting the travel of the anti-rotation limit bar within the long slots. There are two micro switches, which are fixed to the anti-rotation limit side plate 4 by D screws 16. The side of the micro switch 10 does not protrude above the inner side of the corresponding position of the rectangular slot of the anti-rotation limit side plate 4. When the frequency tuning mechanism is running, the tuning capacitor plate moves to the innermost and outermost limit positions, and the anti-rotation limit bar can hit the corresponding micro switch contacts. At this time, the micro switch 10 sends a signal to the system that it has reached the limit position on the corresponding side, and controls the lead screw to stop moving forward.

[0024] Furthermore, the transition flange 102 has four threaded holes on its end face for connecting and fixing a linear stepper motor; and two threaded holes on each of its two sides for connecting and fixing two anti-rotation limiting side plates.

[0025] Furthermore, a through hole is provided in the center of the tuning capacitor plate 2 to avoid forming a closed space that would make vacuum pumping difficult.

[0026] Furthermore, the main vacuum chamber simulator 5 is an accelerator vacuum, and for high-frequency cavities, the main vacuum chamber is a well grounded component; screw B and washer A fix the vacuum-sealed bellows assembly to the main vacuum chamber simulator.

[0027] Advantages and effects of the present invention

[0028] 1. This invention utilizes a folded-back bellows structure, resulting in a compact assembly that occupies minimal space, meeting the requirements of small-sized desktop cyclotrons and also applicable to other small, low-power cyclotrons. Specifically, the folded-back bellows structure comprises four components welded together: a vacuum-sealed grounding cylinder 101, a transition flange 102, a welded bellows 103, and a connecting inner core 104. These four components are arranged to form the folded-back bellows structure, with the welded bellows 103 located inside the vacuum-sealed grounding cylinder 101. A linear stepper motor 7 is directly mounted on the threaded hole at the end face of the transition flange 102. The linear stepper motor 7 extends its lead screw to the left and is located inside the bellows, directly fixed to the connecting inner core. This solves the problem that existing high-frequency cavity frequency tuning mechanisms are too large and unsuitable for the limited space requirements of desktop cyclotrons.

[0029] 2. The present invention provides two grooves on the flange at the left end of the bellows, and the inner groove is filled with an elastic wire mesh (9). The elastic wire mesh (9) is located inside the O-ring seal, which avoids the high-frequency electric field from causing arcing and damage to the O-ring seal by passing through the O-ring seal. This effectively protects the vacuum seal and solves the problem of mechanical damage caused by grounding of the tuning capacitor board, which is difficult to solve in the prior art.

[0030] 3. By setting an adjustable T range on the lead screw and setting a through hole in the center of the tuning capacitor plate to form a vacuum channel, this invention not only eliminates the hidden danger of vacuuming difficulties caused by the closed space of the gasket screw, but also further opens a vacuum channel in the closed space of the thread bottom hole. This solves the problems of existing technology, such as the need to replace the adjustment gasket of different thicknesses, the reduction of local vacuum in a certain area, and the possibility of local arcing or even electron multiplication effect when the vacuum is low, which may cause unstable operation of the equipment. Attached Figure Description

[0031] Figure 1 A cross-sectional schematic diagram of a high-frequency cavity frequency tuning mechanism for a desktop cyclotron accelerator according to the present invention;

[0032] Figure 2 Top view of a desktop cyclotron high-frequency cavity frequency tuning mechanism according to the present invention;

[0033] Figure 3 Isometric schematic diagram of a high-frequency cavity frequency tuning mechanism for a desktop cyclotron accelerator according to the present invention;

[0034] Figure 4 Front view of a high-frequency cavity frequency tuning mechanism for a desktop cyclotron accelerator according to the present invention;

[0035] Figure 5 Right view of a desktop cyclotron high-frequency cavity frequency tuning mechanism according to the present invention;

[0036] Figure 6 A three-dimensional schematic diagram of a high-frequency cavity frequency tuning mechanism for a desktop cyclotron accelerator according to the present invention;

[0037] Figure 7 An isometric view of the vacuum-sealed bellows assembly in this invention;

[0038] Figure 8 A cross-sectional schematic diagram A of the vacuum-sealed bellows assembly in this invention;

[0039] Figure 9 Schematic diagram B of the cross-sectional view of the vacuum-sealed bellows assembly in this invention;

[0040] Figure 10 A cross-sectional schematic diagram of the welded bellows in this invention;

[0041] Figure 11 An isometric schematic diagram of the linear stepper motor of this invention;

[0042] Figure 12 Isometric schematic diagram of the anti-rotation limiting side plate in this invention;

[0043] Figure 13 An isometric view of the anti-rotation limiting strip in this invention;

[0044] Figure 14 This is a schematic diagram illustrating the connection between existing technology and its external ground potential component via beryllium copper finger-shaped springs.

[0045] Figure 15 This is a schematic diagram of the existing technology that connects the back of the tuning capacitor board to an external ground potential component using copper foil and adjusts the cavity resonant frequency by changing the thickness of the adjustment pad.

[0046] Reference numerals: 1. Vacuum-sealed bellows assembly, 101. Vacuum-sealed grounding cylinder, 102. Transition flange, 103. Welded bellows, 104. Connecting inner core, 2. Tuning capacitor plate, 3. Anti-rotation limiting strip, 4. Anti-rotation limiting side plate, 5. High-frequency cavity D-plate simulation component, 6. Main vacuum chamber simulation component, 7. Linear stepper motor, 701. Lead screw, 8. O-ring seal, 9. Elastic wire mesh, 10. Micro switch, 11. Screw A, 12. Screw B, 13. Washer A, 14. Screw C, 15. Washer B, 16. Screw D, 17. Screw E, 18. Washer C. Detailed Implementation

[0047] Design principle of the invention

[0048] 1. Grounding Design Principle of Tuning Capacitor Board without Mechanical Wear: The innovation of this invention lies in the combination of two aspects: on the one hand, it achieves zero mechanical wear, and on the other hand, it solves the problem of arcing and burning of the O-ring seal at the O-ring seal inside the corrugated pipe flange. Both are indispensable and represent the combined effect. First, the design of zero mechanical wear: 1) The grounding method of this invention without mechanical wear: During the grounding process of the tuning capacitor board 2, dynamic grounding of the tuning capacitor board is achieved by changing the compression of the welded corrugated pipe 103. The tuning capacitor board 2, the connecting inner core 104, and the left end of the welded corrugated pipe 103 are always in translational motion, but the right end of the connecting corrugated pipe 103, the transition flange 102, the vacuum-sealed grounding cylinder 101, the elastic wire mesh 9, and the main vacuum chamber simulation component 6 are always stationary. The tuning capacitor board achieves translational motion through the change in the compression of the welded corrugated pipe 103, thereby achieving grounding without mechanical wear. The tuning capacitor board achieves good grounding by connecting the inner core 104, welded bellows 103, transition flange 102, vacuum-sealed grounding cylinder 101, elastic wire mesh 9, B screw 12, A washer 13, and main vacuum chamber simulation component 6. 2) Design to solve the problem of arcing at the O-ring seal. The present invention has two grooves on the flange end face of the left end of the vacuum-sealed grounding cylinder 101. The inner groove is filled with elastic wire mesh 9, and the outer groove is filled with O-ring seal 8. The elastic wire mesh 9 is located inside the O-ring seal, which avoids arcing caused by the high-frequency electric field passing through the O-ring seal position and damaging the O-ring seal, thus effectively protecting the vacuum seal. The elastic wire mesh 9 and the O-ring seal are both elastic, but they are different in physical location and material. The elastic wire mesh 9 is positioned at the front and has good conductivity, which can effectively achieve a good high-frequency electrical connection between the vacuum-sealed grounding cylinder 101 and the main vacuum chamber simulation component 6, so that the high-frequency electric field will not reach the outer O-ring seal, thus effectively protecting the rubber O-ring seal.

[0049] In summary, the innovation lies in the combination of the two: no mechanical wear is the foundation, and the double-layer groove is the guarantee. If we rely solely on no mechanical wear, although there will be no more wear and breakage, the O-ring seal at the left flange of the vacuum-sealed grounding cylinder may be damaged by arcing due to sparking. Conversely, if there is only a double-layer groove without the foundation of no mechanical wear, then the double-layer groove is useless.

[0050] 2. Compact, Small-Size High-Frequency Cavity Frequency Tuning Mechanism Design Principle: The innovation lies in the clever use of the bellows space by the linear stepper motor 7. The lead screw of the linear stepper motor 7 is located inside the bellows and directly fixed to the connecting inner core 104. Furthermore, the flange at the right end of the bellows is directly connected to the linear stepper motor 7, eliminating other functional components found in existing technologies. This reduces the length of the tuning mechanism to a fraction of its original size, effectively saving space and meeting the space-saving requirements of desktop cyclotron accelerators.

[0051] 3. Design principle of the lead screw being positioned at an appropriate midpoint of its translational stroke during cavity resonance. 1) The purpose of setting the distance T is to define an adjustable range for the lead screw position. Since the lead screw is not precisely positioned at the midpoint of its translational stroke during cavity resonance, adjustment is required. This adjustment necessitates a variable connection distance between the lead screw and the tuning capacitor plate, ensuring appropriate adjustment in both directions of the tuning motion. Therefore, during tuning, the lead screw should be positioned at an appropriate midpoint of its stroke; this is how the adjustable amount T of the lead screw connection is defined. 2) Existing methods for replacing the adjustment shim include... Figure 14 As shown: A hole is drilled in the center of the tuning capacitor plate and the adjustment pad, and a threaded hole is provided at the end of the movable rod. The tuning capacitor plate and the adjustment pad are fixed to the end of the movable rod by screws. When changing the adjustment pad of different thickness, it is sometimes necessary to change the screws of different lengths. Moreover, this structure makes it difficult to evacuate the vacuum in the closed space of the threaded bottom hole, which will reduce the local vacuum degree in this area. This area is a high-voltage radio frequency area. When the vacuum degree is low, it may cause local arcing or even generate electron multiplication effect, which will make the equipment unstable; 3) As the present invention is Figure 1 As shown, firstly, since there is no need for adjusting shims, there is also no need for screws to tighten and fix the adjusting shims. The problem of difficulty in vacuuming the closed space of the threaded bottom hole is alleviated when screws are not needed. Secondly, although the screw in the center of the tuning capacitor board is removed, the threaded hole in the center of the tuning capacitor board remains, and the threaded bottom hole is still a closed space. Complete vacuuming requires creating a vacuum channel within this closed space. The purpose of this invention in setting a through hole in the center of the tuning capacitor board is to form a vacuum channel, thus avoiding the difficulty of vacuuming caused by the formation of a closed space. Therefore, eliminating the screw and setting a through hole in the center of the tuning capacitor board are complementary and indispensable.

[0052] Based on the above-mentioned inventive principles, this invention designs a desktop cyclotron high-frequency cavity frequency tuning mechanism.

[0053] A desktop cyclotron high-frequency cavity frequency tuning mechanism, such as Figure 1 , Figure 2As shown, the system includes: arranged horizontally from right to left or from left to right: a high-frequency cavity D-plate simulator 5, a tuning capacitor plate 2, a main vacuum chamber simulator 6, a vacuum-sealed bellows assembly 1, a linear stepper motor 7 with a lead screw, an anti-rotation limiting strip 3, and an anti-rotation limiting side plate 4; the main vacuum chamber simulator 6, the vacuum-sealed bellows assembly 1, the linear stepper motor 7, the anti-rotation limiting strip 3, and the anti-rotation limiting side plate 4 are combined with an O-ring seal 8, an elastic wire mesh 9, a micro switch 10, an A screw 11, a B screw 12, an A washer 13, a C screw 14, a B washer 15, a D screw 16, an E screw 17, and a C washer 18 to drive the tuning capacitor plate 2 to move axially, thereby adjusting the surface distance between the tuning capacitor plate 2 and the high-frequency cavity D-plate simulator 5, and adjusting the surface distance to adjust the frequency of the high-frequency cavity;

[0054] Its features are:

[0055] The vacuum-sealed bellows assembly 1 is provided with a connecting inner core 104. One end of the connecting inner core 104 extends into the vacuum-sealed bellows assembly 1 along the axial direction, and the other end extends into the main vacuum chamber simulation component 6. The connecting inner core 104 is provided with two internal threaded holes. The two internal threaded holes are not drilled through. One internal threaded hole is engaged with the external thread at one end of the lead screw of the linear stepper motor 7, and the other internal threaded hole is engaged with the external thread of the tuning capacitor plate 2.

[0056] Additional notes:

[0057] The reason for not drilling through the two internal threaded holes is to ensure that the inside of the bellows is filled with air while the outside is a vacuum. If the two internal threaded holes were drilled through, the air inside the bellows would be connected to the vacuum outside. Therefore, the design avoids drilling through the two internal threaded holes.

[0058] The linear stepper motor 7 is a hollow motor with a nut at the center of its rotor. A lead screw is screwed into the center of the nut. The lead screw is located inside the bellows and is directly fixed to the connecting inner core 104. The rotation of the motor rotor drives the nut to rotate. The external thread at the left end of the lead screw has the same specification as the internal thread at the right end of the connecting inner core 104. A part of the left end of the lead screw is screwed into the connecting inner core 104 to achieve the connection between the two.

[0059] The right end of the tuning capacitor plate 2 is provided with an external thread, which is fixed to the connecting inner core 104 by the threaded connection. The two surfaces are tightly and well bonded, realizing high-frequency electrical connection without mechanical movement loss, which is conducive to the long-term stable operation of the equipment.

[0060] The vacuum-sealed bellows assembly 1 includes: a vacuum-sealed grounding cylinder 101, a transition flange 102, a welded bellows 103, and a connecting inner core 104. The four parts are welded together to form the vacuum-sealed bellows assembly 1, and the four parts form a good high-frequency electrical connection at their ends.

[0061] The elastic wire mesh 9 is made of beryllium copper, which has good elasticity and conductivity. It is installed in the inner groove of the vacuum-sealed grounding cylinder 101. The beryllium copper wire mesh enables a good high-frequency electrical connection between the vacuum-sealed corrugated pipe assembly 1 and the main vacuum chamber simulation component 5.

[0062] The depth to which the lead screw of the linear stepper motor 7 is screwed into the connecting inner core is adjustable, and the distance T between the right end face of the connecting inner core 104 and the threaded step surface of the lead screw is variable: by setting and adjusting an appropriate distance T, the lead screw can be positioned at an appropriate position in the middle of the effective stroke of the tuning mechanism when the tuning capacitor plate is in the cavity resonance position.

[0063] Furthermore, such as Figure 2 , Figure 3 As shown, the transition flange 102 of the vacuum-sealed bellows assembly 1 has 4 threaded holes on its end face for connecting and fixing the linear stepper motor 7; the two sides of the transition flange 102 each have 2 threaded holes for connecting and fixing 2 anti-rotation limiting side plates 4; the welded bellows 103 has good axial elastic deformation capability and can achieve large axial elastic deformation while maintaining vacuum sealing.

[0064] Furthermore, such as Figure 1 As shown, the left flange end face of the vacuum-sealed grounding cylinder 101 is provided with two grooves, and the inner groove is filled with an elastic wire mesh 9. The elastic wire mesh 9 can realize a reliable high-frequency electrical connection between the left flange of the vacuum-sealed grounding cylinder 101 and the main vacuum chamber simulation component 6. It is located inside the O-ring seal, which avoids the high-frequency electric field from passing through the O-ring seal position and causing arcing and damage to the O-ring seal, thereby effectively protecting the vacuum seal component.

[0065] Furthermore, such as Figure 1 As shown, the linear stepper motor 7 is directly installed in the threaded hole on the end face of the transition flange 102; a local distributed capacitance of the cavity is formed between the opposite surfaces of the tuning capacitor plate 2 and the high-frequency cavity D plate simulation component 5. The value of this local distributed capacitance is changed by changing the distance L between the two surfaces, thereby changing the resonant frequency of the cavity.

[0066] Furthermore, such as Figure 1 , Figure 3 As shown, there are two anti-rotation limiting side plates 4, one end of which has two through holes and the other end has a rectangular groove structure inside; they are fixed to both sides of the transition flange 102 by E screws 17 and C washers 18.

[0067] Furthermore, the anti-rotation limiting strip 3 is long and has a through hole in the middle. At one end concentric with the through hole, there is a racetrack-shaped stepped recessed structure. The two ends of the anti-rotation limiting strip 3 are inserted into the long grooves of the two anti-rotation limiting side plates 4. At this time, the range of motion of the anti-rotation limiting strip 3 in the long groove corresponds exactly to the required range of motion of the tuning capacitor plate.

[0068] Furthermore, such as Figure 3 , Figure 11 , Figure 13 As shown, the end of the lead screw of the linear stepper motor 7 has a symmetrical planar structure. The anti-rotation limiting strip 3 is connected and fixed to the right end of the lead screw by screw A 11. Figure 13 As shown, the recessed part of the connecting fixing strip 3 is exactly with Figure 11 The right end of the lead screw is partially removed to accommodate this; for example... Figure 3 As shown, the front and rear ends of the anti-rotation limiting strip 3 are inserted into the long grooves of the two anti-rotation limiting side plates 4; as Figure 2 As shown, the linear stepper motor 7 is fixed to the transition flange 102 by C screw 14 and B washer 15.

[0069] Furthermore, such as Figure 3 As shown, the right end structure of the linear stepper motor 7 lead screw, the anti-rotation limiting strip 3, the long slot structure of the anti-rotation limiting side plate 4, and the micro switch 10 are combined to achieve a combination of lead screw anti-rotation and translation limiting structure: the right end of the lead screw has an internal thread and a symmetrical planar structure at the end. The anti-rotation limiting strip 3 is connected and fixed to the right end of the lead screw by screw A 14. The concave part of the anti-rotation limiting strip 3 is exactly adapted to the planar structure formed by removing the part of the right end of the lead screw, and the two cannot rotate relative to each other. The two ends of the anti-rotation limiting strip 3 are inserted into the long slots of the two anti-rotation limiting side plates 4. When the equipment is running, the anti-rotation limiting strip 3 cannot rotate in any direction. The movement of the anti-rotation limit bar 3 prevents the lead screw from rotating. Simultaneously, because both ends of the anti-rotation limit bar 3 are inserted into the long slots of the two anti-rotation limit side plates, the travel of the anti-rotation limit bar is restricted within these slots. Two microswitches are fixed to the anti-rotation limit side plate 4 using D-screws 16. The side of the microswitch 10 does not protrude beyond the inner side of the corresponding position of the rectangular slot in the anti-rotation limit side plate 4. When the frequency tuning mechanism is running, if the tuning capacitor plate moves to its innermost and outermost limit positions, the anti-rotation limit bar can strike the corresponding microswitch contacts. At this time, the microswitch 10 sends a signal to the system indicating that it has reached the corresponding limit position, preventing the lead screw from continuing to move forward.

[0070] Furthermore, the transition flange 102 has four threaded holes on its end face for connecting and fixing a linear stepper motor; and two threaded holes on each of its two sides for connecting and fixing two anti-rotation limiting side plates.

[0071] Furthermore, a through hole is provided in the center of the tuning capacitor plate 2 to avoid forming a closed space that would make vacuum pumping difficult.

[0072] Furthermore, the main vacuum chamber simulator 6 is an accelerator vacuum, and for high-frequency cavities, the main vacuum chamber is a well grounded component; screw B and washer A fix the vacuum-sealed bellows assembly to the main vacuum chamber simulator.

[0073] It should be emphasized that the above specific embodiments are merely explanations of the present invention and are not intended to limit the invention. The invention can be used in desktop cyclotrons as well as other small, low-power cyclotrons. After reading this specification, those skilled in the art can make modifications to the above embodiments without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A desktop cyclotron high-frequency cavity frequency tuning mechanism, comprising: Along the horizontal direction from right to left or from left to right: High-frequency cavity D-plate simulation component (5), tuning capacitor plate (2), main vacuum chamber simulation component (6), vacuum sealing bellows assembly (1), linear stepper motor with lead screw (7), anti-rotation limit strip (3), anti-rotation limit side plate (4). The main vacuum chamber simulator (6), vacuum sealing bellows assembly (1), linear stepper motor (7), anti-rotation limit strip (3), anti-rotation limit side plate (4), O-ring seal (8), elastic wire mesh (9), micro switch (10), A screw (11), B screw (12), A washer (13), C screw (14), B washer (15), D screw (16), E screw (17), and C washer (18) are combined together to drive the tuning capacitor plate (2) to move along the axial direction, thereby adjusting the surface distance between the tuning capacitor plate (2) and the high-frequency cavity D plate simulator (5). The frequency of the high-frequency cavity is adjusted by adjusting this surface distance. Its features are: The vacuum-sealed bellows assembly (1) is provided with a connecting core (104). The connecting core (104) extends axially, with one end extending into the vacuum-sealed bellows assembly (1) and the other end extending into the main vacuum chamber simulation component (6). The connecting core (104) is provided with two internal threaded holes. The two internal threaded holes are not drilled through. One internal threaded hole is engaged with the external thread of one end of the linear stepper motor (7) screw, and the other internal threaded hole is engaged with the external thread of the tuning capacitor plate (2). The linear stepper motor (7) is a hollow motor with a nut at the center of its rotor. The nut is screwed into the center of the lead screw. The lead screw is located inside the bellows and is directly fixed to the connecting inner core (104). The rotation of the motor rotor drives the nut to rotate. The external thread at the left end of the lead screw has the same specification as the internal thread at the right end of the connecting inner core (104). A part of the left end of the lead screw is screwed into the connecting inner core (104) to achieve the connection between the two. The right end of the tuning capacitor plate (2) is provided with an external thread, which is fixed to the connecting inner core (104) by the thread connection. The two surfaces are tightly and well bonded, realizing high-frequency electrical connection, and there is no mechanical movement loss, which is conducive to the long-term stable operation of the equipment. The vacuum-sealed bellows assembly (1) includes: a vacuum-sealed grounding cylinder (101), a transition flange (102), a welded bellows (103), and a connecting inner core (104). The four pieces are welded together to form the vacuum-sealed bellows assembly (1), and the four pieces form a good high-frequency electrical connection at their ends. The main vacuum chamber simulator (6) is at a good high-frequency ground potential in the accelerator. The elastic wire mesh (9) is made of beryllium copper material, which has good elasticity and conductivity. It is installed in the inner groove of the vacuum-sealed grounding cylinder (101). The beryllium copper wire mesh enables a good high-frequency electrical connection between the vacuum-sealed corrugated pipe assembly (1) and the main vacuum chamber simulator (6). The depth to which the lead screw of the linear stepper motor (7) is screwed into the connecting inner core is adjustable, and the distance T between the right end face of the connecting inner core (104) and the threaded step surface of the lead screw is variable: by setting and adjusting an appropriate distance T, the lead screw can be positioned at an appropriate position in the middle of the effective stroke of the tuning mechanism when the tuning capacitor plate is in the cavity resonance position.

2. The desktop cyclotron high-frequency cavity frequency tuning mechanism according to claim 1, characterized in that, The transition flange (102) end face of the vacuum-sealed bellows assembly (1) is provided with 4 threaded holes for connecting and fixing the linear stepper motor (7); the two sides of the transition flange (102) are each provided with 2 threaded holes for connecting and fixing 2 anti-rotation limiting side plates (4); the welded bellows (103) has good axial elastic deformation capability and can achieve axial elastic deformation while maintaining vacuum sealing.

3. The desktop cyclotron high-frequency cavity frequency tuning mechanism according to claim 1, characterized in that, The left flange end face of the vacuum sealing grounding cylinder (101) is provided with two grooves. The inner groove is filled with an elastic wire mesh (9). The elastic wire mesh (9) can realize a reliable high-frequency electrical connection between the left flange of the vacuum sealing grounding cylinder (101) and the main vacuum chamber simulation component (6). It is located inside the O-ring seal, which avoids the high-frequency electric field from passing through the O-ring seal position and causing arcing and damage to the O-ring seal, thereby effectively protecting the vacuum sealing component.

4. The desktop cyclotron high-frequency cavity frequency tuning mechanism according to claim 1, characterized in that, The linear stepper motor (7) is directly installed in the threaded hole on the end face of the transition flange (102); a local distributed capacitance of the cavity is formed between the opposite face of the tuning capacitor plate (2) and the high-frequency cavity D plate simulation component (5). The value of the local distributed capacitance is changed by changing the distance L between the two faces, thereby changing the resonant frequency of the cavity.

5. The desktop cyclotron high-frequency cavity frequency tuning mechanism according to claim 1, characterized in that, The anti-rotation limiting side plate (4) consists of two pieces, one end of which has two through holes and the other end has a rectangular groove structure inside; it is fixed to both sides of the transition flange (102) by E screws (17) and C washers (18); The anti-rotation limiting strip (3) is long and has a through hole in the middle. At one end concentric with the through hole, there is a racetrack-shaped step-down structure. The two ends of the anti-rotation limiting strip (3) are inserted into the long grooves of the two anti-rotation limiting side plates (4). At this time, the movement range of the anti-rotation limiting strip (3) in the long groove corresponds exactly to the movement range required by the tuning capacitor plate.

6. The desktop cyclotron high-frequency cavity frequency tuning mechanism according to claim 1, characterized in that: The linear stepper motor (7) has a symmetrical planar structure at the end of the lead screw. The anti-rotation limiting strip (3) is connected and fixed to the right end of the lead screw by screw A (11). The recessed part of the anti-rotation limiting strip (3) is exactly adapted to the part removed from the right end of the lead screw. The front and rear ends of the anti-rotation limiting strip (3) are inserted into the long grooves of two anti-rotation limiting side plates (4). The linear stepper motor (7) is fixed to the transition flange (102) by screw C (14) and washer B (15).

7. The desktop cyclotron high-frequency cavity frequency tuning mechanism according to claim 1, characterized in that: By combining the right end structure of the linear stepper motor (7) lead screw, the anti-rotation limiting strip (3), the long slot structure of the anti-rotation limiting side plate (4), and the micro switch (10), a combination of lead screw anti-rotation and translation limiting structure is achieved: the right end of the lead screw is provided with an internal thread and a symmetrical planar structure at the end. The anti-rotation limiting strip (3) is connected and fixed to the right end of the lead screw by screw A (11). The concave part of the anti-rotation limiting strip (3) is exactly adapted to the planar structure formed by removing the part of the right end of the lead screw. The two cannot rotate relative to each other. The two ends of the anti-rotation limiting strip (3) are inserted into the long slots of the two anti-rotation limiting side plates (4). When the equipment is running, the anti-rotation limiting strip (3) cannot rotate in the angular direction, so the lead screw cannot rotate; at the same time, because the anti-rotation limiting strip (3) The two ends are inserted into the long slots of the two anti-rotation limiting side plates, and the stroke of the anti-rotation limiting strip is limited within the long slots; there are two micro switches, which are installed and fixed on the anti-rotation limiting side plate (4) by D screws (16). The side of the micro switch does not protrude above the inner side of the corresponding position of the rectangular slot of the anti-rotation limiting side plate (4); when the frequency tuning mechanism is running, the tuning capacitor plate moves to the innermost and outermost limit positions, the anti-rotation limiting strip can hit the corresponding micro switch contacts respectively. At this time, the micro switch (10) sends a signal to the system that it has reached the limit position on the corresponding side, and the control screw cannot continue to move forward; through the combined use of the right end structure of the screw, the anti-rotation limiting strip, and the long slot structure of the anti-rotation limiting side plate, the combination of screw anti-rotation and translation limiting structure is realized.

8. The desktop cyclotron high-frequency cavity frequency tuning mechanism according to claim 1, characterized in that: The transition flange (102) has four threaded holes on its end face for connecting and fixing a linear stepper motor; and two threaded holes on each side for connecting and fixing two anti-rotation limiting side plates.

9. The desktop cyclotron high-frequency cavity frequency tuning mechanism according to claim 1, characterized in that: The tuning capacitor plate (2) has a through hole in the center to avoid forming a closed space that would make vacuum pumping difficult.

10. The desktop cyclotron high-frequency cavity frequency tuning mechanism according to claim 1, characterized in that: The main vacuum chamber simulator (6) is an accelerator vacuum. For high-frequency cavities, the main vacuum chamber is a good grounding component. Screw B and washer A fix the vacuum-sealed bellows assembly to the main vacuum chamber simulator.

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