Interpolation split magnet supporting structure

Abstract

The invention discloses an interpolated split magnet supporting structure. The interpolated split magnet supporting structure comprises a split magnet, an interpolated central cylinder and an interpolated magnet supporting structure, the split magnet is fixedly placed in the vacuum chamber of the interpolated magnet supporting structure through the low-temperature cold-contraction flexible compensation structure, and the split magnet and the interpolated magnet supporting structure fall into the center position of the cylinder body in the axis direction of the interpolated center cylinder through installation equipment and are accurately positioned. The inserted split magnet structure is circumferentially fixed by adjusting and tensioning the locking wedge block structure, and circumferential deflection of the inserted split magnet caused by the influence of electromagnetic force under the back field condition is limited. The two ends of the interpolated magnet supporting structure fix the interpolated magnet to the interpolated center cylinder in the axial direction through a pull rod and a fixing plate, and the interpolated split magnet is axially fixed in the back field magnet system. According to the invention, the high-precision requirement of coaxial installation of the symmetric split magnet can be effectively met.

Description

Technical Field

[0001] This invention relates to the field of low-temperature performance testing of superconducting conductors and superconducting tapes and wires, and specifically to an intercalated split magnet support structure. Background Technology

[0002] With the ever-increasing demand for extremely high magnetic field strength in fields such as high-energy physics and nuclear fusion energy, engineering requirements are being placed on the physical performance of superconducting magnet systems. Superconducting conductors and cables are the key foundations for manufacturing superconducting magnets, and the physical properties of the conductors directly determine the magnetic field strength generated by the superconducting magnet. Testing the physical properties of superconducting conductors and cables, as well as their electrophysical properties under a background magnetic field, are important testing steps for verifying conductor performance. With the technological development of superconducting conductors and the advancement of superconducting materials, there is an urgent need for superconducting magnet systems that can generate extremely high steady-state magnetic fields. A high background magnetic field environment can maximize the testing of key technical parameters of superconducting conductors, such as the critical magnetic field and cyclic degradation performance. For example, the superconducting conductors used in large-scale scientific projects such as the International Thermonuclear Experimental Reactor (ITER) and the Future Circular Collider (FCC) all need to be verified on a platform similar to the Swiss SULTAN test facility, through simulation of real extreme operating conditions to verify their comprehensive mechanical, thermal, and electromagnetic performance. This fully demonstrates that an innovative fixed structure capable of providing sufficient, uniform, and reliable mechanical constraints for the intercalation magnet in extreme multi-field coupling environments has become a common key requirement for overcoming the technological bottlenecks of ultra-high field magnets and promoting the development of related cutting-edge fields. Hybrid magnet technology, which combines intercalation magnets with backfield magnets, has become the mainstream technical path for breaking through the magnetic field limits of single magnets under limited engineering and cost constraints. Among these, the intercalation magnet, as the core component for generating the target ultra-high magnetic field, directly determines the success or failure of the entire hybrid magnet system through its performance and reliability.

[0003] The intercalated magnet operates within a strong background magnetic field of several to tens of Tesla provided by the back field magnet, while simultaneously carrying an extremely high operating current. Therefore, its superconducting conductor will endure extremely harsh conditions involving multi-field coupling, including extremely low temperatures, strong magnetic fields, large currents, and enormous electromagnetic forces (Lorentz forces). This combined load generates electromagnetic stresses of up to hundreds of megapascals within the magnet, potentially leading to micrometer-level displacement or vibration in the conductor. Solving the structural displacement and deflection of the intercalated magnet under back field conditions, and achieving a stable and reliable intercalated magnet fixing structure, is a pressing problem for current superconducting hybrid magnet systems. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an intercalated split magnet support structure. The split magnet consists of two symmetrically arranged magnets, and the split space formed between the two magnets can be used for extreme low-temperature physical performance testing of superconducting conductors and superconducting cables. This invention provides stable and reliable structural support for the intercalated split magnet system, achieving high-precision coaxiality of the two split magnets through component positioning structures. The support structure uses tie rods to statically fix the split magnets axially to the intercalated central cylinder, and uses locking wedges to constrain and fix the split magnets circumferentially to the intercalated central cylinder, overcoming positional displacement of the intercalated split magnets under the influence of the back field magnet, ensuring the safe operation of the hybrid superconducting magnet system, and effectively suppressing the effects of structural shrinkage deformation of the split magnet system under low-temperature conditions. This invention simultaneously considers high reliability and process feasibility, providing a reliable mechanical solution for manufacturing next-generation ultra-high field intercalated superconducting magnets with higher performance and greater stability.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An internal splitting magnet support structure includes two symmetrically arranged splitting magnets, two vacuum chambers, a conductor pad, an internal central cylinder, a fixing plate, a tie rod, and a locking wedge structure. Each vacuum chamber includes a vacuum shell and a vacuum chamber flange. The splitting magnet is placed inside the vacuum shell, and the vacuum chamber flange is welded to the end of the vacuum shell. A flexible compensation structure is disposed between the end of the splitting magnet and the vacuum chamber flange to press and fix the splitting magnet. The conductor pad is disposed between the two vacuum chambers, and the positioning step of the conductor pad cooperates with the positioning groove on the end face of the vacuum shell to achieve positioning assembly. The fixing plate is welded and fixed to the internal central cylinder. At the end of the core cylinder; both ends of the tie rod are connected to the fixing plate and the vacuum chamber flange respectively through nuts, axially fixing the vacuum chamber to the inner core cylinder; the locking wedge structure includes a fixed wedge, a sliding wedge, a tensioning ring, a pre-tensioning spring and a tensioning rod. The fixed wedge is welded to the outer wall of the vacuum chamber through a washer, the sliding wedge is connected to the end face of the vacuum chamber flange through the tensioning rod, the pre-tensioning spring connects the tensioning ring to the outer wall of the vacuum chamber, and the inclined surfaces on both sides of the tensioning ring are in frictional engagement with the tapered inclined surfaces of the fixed wedge and the sliding wedge. By adjusting the tensioning rod, the tensioning ring expands radially and fits tightly against the inner wall of the inner core cylinder to achieve circumferential fixation.

[0007] Furthermore, a conductor pad is provided between the two vacuum chambers, and the two are positioned and installed by a positioning step and fastened by four screws, thus fixing the two split magnets and their vacuum chambers together as a whole.

[0008] Furthermore, after the splitting magnet and flexible compensation structure are placed in the vacuum shell, the splitting magnet and flexible compensation structure are pressed together by the vacuum chamber flange. Then, the vacuum chamber flange and the vacuum shell are sealed and welded to form a vacuum chamber. A fixing plate is welded to the end of the inner insert center cylinder. One end of the tie rod is connected to the fixing plate, and the other end is connected to the vacuum chamber flange, fixing the vacuum chamber axially to the inner insert center cylinder to prevent the splitting magnet from moving axially under the action of the back field magnet.

[0009] Furthermore, the locking wedge structure includes a fixed wedge, a sliding wedge, a tensioning ring, a preload spring, a tensioning rod, and a small disc spring assembly. The fixed wedge is welded to the outer wall of the vacuum chamber via a washer, and the sliding wedge is connected to the flange end face of the vacuum chamber via the tensioning rod and the small disc spring assembly. Both the fixed wedge and the sliding wedge have a tapered inclined surface structure on one side, forming a V-groove, for mechanical engagement with the inclined surface structure of the tensioning ring.

[0010] Furthermore, the two ends of the tensioning ring are connected to the outer circumferential wall of the vacuum chamber by pre-tensioning springs, and the two sides of the tensioning ring are V-shaped inclined structures that cooperate with the V-shaped grooves formed by the fixed wedge and the sliding wedge.

[0011] Furthermore, when the splitting magnet and the inner splitting magnet support structure are assembled with the inner central cylinder, the tension rod is released, the V-groove spacing formed by the fixed wedge and the sliding wedge increases, and the tension ring contracts towards the outer wall of the cylinder under the tension of the pre-tension spring, so that the outer diameter of the tension ring is smaller than the inner diameter of the inner central cylinder, and the two are assembled with a gap to prevent the inner splitting magnet support structure from getting stuck during the assembly process with the inner central cylinder.

[0012] Furthermore, when placing the splitting magnet and the inner splitting magnet support structure together in the designed assembly position of the inner central cylinder, a tensioning rod is tightened using a tool. During the tightening process, the movable wedge moves along the axis of the inner central cylinder, reducing the V-groove spacing formed by the fixed and sliding wedges. As the V-groove spacing decreases, the inclined surfaces on both sides of the tensioning ring slide on the tapered inclined surfaces of the fixed and sliding wedges and expand radially outward along the inner central cylinder. When the tensioning ring is tightly fitted against the inner wall of the inner central cylinder to form a locking mechanism, a nut is used to lock the tensioning rod on the vacuum chamber flange.

[0013] Furthermore, the expanded-diameter tensioning ring secures the splitting magnet and the internal splitting magnet support structure to the inner cavity of the internal central cylinder, preventing the splitting magnet from shifting circumferentially under the action of the back field magnet.

[0014] Furthermore, the internal split magnet support structure will undergo structural shrinkage deformation after the magnet cools down. The small disc spring assembly uses the compressibility of the disc spring to compensate for the tension of the tension rod, preventing the vacuum chamber from loosening due to the shrinkage deformation of the locking wedge block structure.

[0015] Beneficial effects:

[0016] 1. The present invention, through the positioning structure design of vacuum shell and conductor pad, enables a pair of symmetrically arranged split magnets to achieve high-precision coaxiality and reduces the center magnetic field error of the symmetrically arranged split magnets.

[0017] 2. The present invention employs a flexible compensation structure that can structurally compress the splitting magnet placed inside the vacuum chamber, while utilizing the compressibility of the disc spring assembly of the flexible compensation structure to compensate for the structural shrinkage of the splitting magnet under low-temperature conditions.

[0018] 3. The locking wedge structure of the present invention is in a released state during the assembly process of the inner splitting magnet and the inner central cylinder. The maximum assembly outer diameter of the inner splitting magnet support structure is smaller than the inner diameter of the inner central cylinder, so that the inner splitting magnet support structure and the inner central cylinder are prevented from structurally jamming during the assembly process.

[0019] 4. When the present invention is placed inside the designed inner center cylinder, the inner splitting magnet support structure is firmly attached to the inner wall of the inner center cylinder by adjusting the locking wedge block structure and forming a circumferential fixation, so as to prevent the splitting magnet from shifting under the action of the back field magnet. Attached Figure Description

[0020] Figure 1 This is an overall structural diagram of the high-field conductor testing device involved in the present invention;

[0021] Figure 2 This is a diagram of the internal splitting magnet support structure and the internal central cylinder structure of the present invention;

[0022] Figure 3 This is a structural diagram of the intercalated split magnet support structure of the present invention;

[0023] Figure 4 This is a cross-sectional view of the intercalated split magnet support structure of the present invention;

[0024] Figure 5 This is a diagram of the flexible compensation structure of the present invention;

[0025] Figure 6 This is a structural diagram of the conductor pad of the present invention;

[0026] Figure 7 This is a structural diagram of the locking wedge block of the present invention;

[0027] Figure 8This is a cross-section of the locking wedge block structure of the present invention.

[0028] The attached figures are labeled as follows: 1-back field magnet, 2-back field magnet structure system, 3-intercalated split magnet support structure, 4-pull rod, 5-fixed plate, 6-locking wedge structure, 7-low temperature return pipe, 8-vacuum electrode, 9-preload spring, 10-conductor pad, 11-low temperature inlet pipe, 12-split magnet, 13-vacuum shell, 14-vacuum chamber flange, 15-flexible compensation structure, 16-compensation guide rod, 17-compression compensation disc spring, 18-positioning step, 19-positioning groove, 20-fixed wedge, 21-tensioning ring, 22-sliding wedge, 23-tensioning pull rod, 24-small disc spring assembly, 25-washer ring, 26-intercalated center cylinder. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0030] like Figure 1 As shown, the high-field conductor testing device involved in this invention includes a back field magnet 1, a back field magnet structure system 2, and an internally inserted split magnet support structure 3. The back field magnet 1 is disposed inside the back field magnet structure system 2 and is the core device for testing superconducting conductors and superconducting cables. The internally inserted split magnet support structure 3 is inserted and placed at the center of the axis formed by the back field magnet 1 and the back field magnet structure system 2. A structural hole is provided at the center of the axis formed by the back field magnet 1 and the back field magnet structure system 2. The internally inserted split magnet support structure 3 needs to be aligned and assembled with the structural hole during insertion.

[0031] The inner central cylinder 26 is fixedly connected to the back field magnet structure system 2. The middle through hole of the inner central cylinder 26 is aligned with the structural hole of the back field magnet structure system 2 and assembled to form a conductor placement cavity for low-temperature physical performance testing of superconducting conductors and superconducting cables.

[0032] The internal splitting magnet support structure 3 of the present invention includes a pull rod 4, a fixing plate 5, a locking wedge block structure 6, a low-temperature return pipe 7, a vacuum electrode 8, a pre-tightening spring 9, a conductor pad 10, a low-temperature inlet pipe 11, a vacuum shell 13, a vacuum chamber flange 14, a flexible compensation structure 15, and an internal central cylinder 26.

[0033] The inserted splitting magnet support structure 3 is placed and fixed at the center of the inserted central cylinder 26. This position is precisely calibrated by the back field magnet 1 after magnetic measurement and aligned with the structural hole.

[0034] like Figure 3 As shown, the pull rod 4 passes through the through hole of the vacuum chamber flange 14 to fix the two vacuum chambers together as a whole, and a conductor pad 10 is provided in the middle of the two vacuum chambers. The two ends of the pull rod 4 are respectively fixedly connected to the fixing plate 5, and the fixing plate 5 is welded to the end of the inner insert central cylinder 26. The locking wedge structure 6 is evenly arranged radially along the vacuum shell 13, and the two ends of the locking wedge structure 6 are constrained and fixed by the pre-tension spring 9 to prevent the locking wedge structure 6 from separating from the vacuum shell 13. The cryogenic return pipe 7 passes through the two vacuum shells 13 and is respectively sealed and welded. The cryogenic return pipe 7 is used for the return of the cryogenic cooling medium of the magnet. The vacuum electrode 8 is respectively welded to the end face of the two vacuum chamber flanges 14 and is used to excite and energize the magnet. The cryogenic inlet pipe 11 passes through the two vacuum shells 13 and is respectively sealed and welded. The cryogenic inlet pipe 11 is used to input the cryogenic cooling medium into the magnet. The cryogenic return pipe 7, vacuum electrode 8, and cryogenic inlet pipe 11 are welded and fixed to the vacuum housing 13 and vacuum chamber flange 14 respectively according to the engineering design, providing excitation current and cryogenic medium for the splitting magnet 12. The vacuum housing 13 and vacuum chamber flange 14 are connected by welding to form a whole vacuum chamber, which vacuum-isolates the splitting magnet 12 from the back field magnet 1. The cryogenic return pipe 7 and cryogenic inlet pipe 11 pass through the two vacuum housings 13 respectively and are sealed by welding; the vacuum electrode 8 is welded to the end face of the two vacuum chamber flanges 14 respectively.

[0035] like Figure 4 As shown, the splitting magnets 12 are placed inside the vacuum housing 13, and the inner end faces of the splitting magnets 12 are axially assembled and fitted with the end faces of the vacuum housing 13. Then, three flexible compensation structures 15 are evenly distributed circumferentially along the outer end faces of the splitting magnets 12. The flexible compensation structures 15 are pressed together using the vacuum chamber flange 14, and the splitting magnets 12 are secured to the inside of the vacuum chamber under the pressing action of the flexible compensation structures 15. Two vacuum electrodes 8 are fixed to the vacuum chamber flange 14 by sealing welding, each providing excitation current to one of the two symmetrically arranged splitting magnets 12. Figure 5As shown, the flexible compensation structure 15 includes a compensation guide rod 16 and a compression compensation disc spring 17. The compression compensation disc spring 17 is composed of multiple standard disc springs in a mating configuration, which not only has a large axial compressive force but also can obtain a large compressive compensation displacement by relying on the mating configuration of the disc springs. The mating disc spring is fitted onto the small-diameter shaft of the compensation guide rod 16 through its inner hole, and the large-diameter shaft of the compensation guide rod 16 is used as a limiting step. The end of the disc spring of the flexible compensation structure 15 contacts the end of the splitting magnet 12, and the end of the guide rod of the flexible compensation structure 15 contacts the vacuum chamber flange 14. During the assembly of the splitting magnet 12, the vacuum chamber flange 14 is pressed along the axial direction of the splitting magnet 12 using external assembly tools, and the compression compensation disc spring 17 forms a large elastic axial force under the compression of external force. When the splitting magnet 12 experiences structural shrinkage under low-temperature conditions, the compressibility of the compressible disc spring 17 is used to compensate for the gap caused by the structural shrinkage, thus making the splitting magnet 12 stable and firm inside the vacuum chamber.

[0036] The two splitting magnets 12 are respectively placed inside two vacuum chambers formed by vacuum shells 13 and vacuum chamber flanges 14, such as Figure 6 , Figure 7 As shown, a conductor pad 10 is provided between the vacuum chambers. The two end faces of the conductor pad 10 are machined with positioning steps 18, and the end face of the vacuum housing is machined with positioning grooves 19. The two vacuum chambers are assembled with high precision coaxiality by using the positioning steps 18 and the positioning grooves 19 of the conductor pad 10.

[0037] After the two vacuum chambers and conductor pad 10 are assembled, the vacuum chambers and conductor pad 10 are fastened into a whole using pull rod 4 and nuts. Simultaneously, both ends of pull rod 4 are connected to fixing plate 5. Fixing plate 5 is fixed to the end of the inner central cylinder 26 by welding. The fixed connection between pull rod 4 and fixing plate 5 axially fixes the splitting magnet 12 in the magnet's axial direction, preventing axial movement of the splitting magnet 12 under the action of the coupling magnet of the back field magnet 1.

[0038] like Figure 7 , Figure 8As shown, the locking wedge structure 6 includes a preload spring 9, a fixed wedge 20, a tension ring 21, a sliding wedge 22, a tension rod 23, a small disc spring assembly 24, and a washer 25. The washer 25 is welded to the outer wall of the vacuum housing 13, and then the fixed wedge 20 is welded and fixed to the designed position on the outer circumferential wall of the washer. The sliding wedge 22 is evenly distributed along the outer circumference of the washer 25, and the tension rod 23 passes through the through hole of the fixed wedge 20. The end of the tension rod 23 is welded and fixed to the sliding wedge 22. Then, the tension rod 23 is fixed and constrained to the vacuum chamber flange 14 using the small disc spring assembly 24 and a standard nut. At this time, the fixed wedge 20 and the sliding wedge 22 are evenly distributed on the outer circumference of the washer 25 and form a V-shaped groove structure. The tensioning ring 21 is placed in the V-shaped groove formed by the fixed wedge block 20 and the sliding wedge block 22 through its two inclined surfaces, and the tensioning ring is tightened by the pre-tensioning spring 9, so that the assembly diameter formed by the tensioning ring 21 is smaller than the inner diameter of the inner insert center cylinder 26, and the two are assembled with a gap to prevent the inner insert split magnet support structure from getting stuck during the assembly process with the inner insert center cylinder.

[0039] The splitting magnet 12 and its internal splitting magnet support structure 3 are placed at the designed position of the internal center cylinder 26. The tensioning rod 23 is tightened along the magnet's axial direction using a tool. During the tightening process of the tensioning rod 23, the distance between the V-shaped grooves formed by the fixed wedge 20 and the sliding wedge 22 decreases, causing the two inclined surfaces of the tensioning ring 21 to slide upwards along the tapered inclined surfaces of the fixed wedge 20 and the sliding wedge 22, thereby expanding the assembly diameter of the tensioning ring and tightly fitting it against the inner wall of the internal center cylinder 26 to form a locking friction. The locking friction between the tensioning ring 21 and the inner wall of the internal center cylinder 26 is used to overcome the axial deflection of the splitting magnet 12 under the electromagnetic coupling effect of the back field magnet 1.

[0040] Under low temperature conditions, the locking wedge structure 6 causes a decrease in the locking friction between the tension ring 21 and the inner central cylinder 26 due to low temperature contraction. The small disc spring assembly 24 uses the compressibility of the disc spring to compensate for the tension of the tension rod 23, preventing the locking wedge structure 6 from contracting and deforming, which could cause loosening between the vacuum chamber and the inner central cylinder 26.

[0041] Those skilled in the art will understand that various changes, modifications, substitutions, and variations can be made to the intercalated split magnet support structure without departing from the principles and spirit of the present invention, and all such modifications based on the present invention should fall within the protection scope of the appended claims.

Claims

1. A support structure for an intercalated split magnet, characterized in that, The system includes two symmetrically arranged splitting magnets, two vacuum chambers, conductor pads, an inner central cylinder, a fixing plate, tie rods, and a locking wedge structure. Each vacuum chamber includes a vacuum shell and a vacuum chamber flange. The splitting magnets are placed inside the vacuum shell, and the vacuum chamber flange is welded to the end of the vacuum shell. A flexible compensation structure is set between the end of the splitting magnet and the vacuum chamber flange to press and fix the splitting magnet. The conductor pads are set between the two vacuum chambers, and the positioning steps of the conductor pads cooperate with the positioning grooves on the end face of the vacuum shell to achieve positioning and assembly. The fixing plate is welded and fixed to the end of the inner central cylinder. The two ends of the rod are connected to the fixing plate and the vacuum chamber flange respectively by nuts, which axially fixes the vacuum chamber to the inner insertion center cylinder; the locking wedge block structure includes a fixed wedge block, a sliding wedge block, a tension ring, a preload spring and a tension rod. The fixed wedge block is welded to the outer wall of the vacuum chamber through a washer ring, the sliding wedge block is connected to the end face of the vacuum chamber flange through the tension rod, the preload spring connects the tension ring to the outer wall of the vacuum chamber, and the inclined surfaces on both sides of the tension ring are in frictional engagement with the tapered inclined surfaces of the fixed wedge block and the sliding wedge block. By adjusting the tension rod, the tension ring expands radially and fits tightly against the inner wall of the inner insertion center cylinder to achieve circumferential fixation.

2. The intercalated split magnet support structure according to claim 1, characterized in that: The flexible compensation structure includes a guide clamping cylinder and a clamping compensation disc spring. The guide clamping cylinder contacts the end of the splitting magnet at the end of the disc spring, and the other end of the disc spring contacts the vacuum chamber flange. The elasticity of the disc spring is used to clamp the splitting magnet and compensate for low-temperature shrinkage deformation.

3. The intercalated split magnet support structure according to claim 1, characterized in that: The conductor pad has positioning steps on both ends and positioning grooves on the end face of the vacuum housing. The positioning steps and positioning grooves cooperate to achieve coaxial assembly of the two vacuum chambers.

4. The intercalated split magnet support structure according to claim 1, characterized in that: The locking wedge structure also includes a small disc spring assembly and a washer. The washer is welded to the outer wall of the vacuum housing, the fixing wedge is welded to the outer wall of the washer, and the small disc spring assembly is installed between the tensioning rod and the vacuum chamber flange.

5. The intercalated split magnet support structure according to claim 1 or 4, characterized in that: The tensioning ring has a two-sided inclined surface design, with the inclined surfaces engaging with the tapered inclined surfaces of the fixed wedge and the sliding wedge respectively to form a V-groove structure.

6. The intercalated split magnet support structure according to claim 1, characterized in that: The tensioning ring contracts inward under the tension of the pre-tensioning spring, making the outer diameter of the tensioning ring smaller than the inner diameter of the inner insert center cylinder, thus forming an assembly gap.

7. The intercalated split magnet support structure according to claim 1 or 6, characterized in that: When the tensioning rod is tightened, the sliding wedge moves axially to reduce the spacing of the V-groove, and the inclined surfaces on both sides of the tensioning ring slide on the tapered inclined surface and expand radially outward, forming a jamming effect by tightly fitting with the inner wall of the inner insert center cylinder.

8. The intercalated split magnet support structure according to claim 4, characterized in that: The disc spring assembly includes two mating disc springs used to compensate for changes in tension of the tension rod caused by low-temperature contraction.

9. The intercalated split magnet support structure according to claim 1, characterized in that: The conductor pad has a test hole in the middle, providing a space for testing the superconducting performance of conductors and superconducting wires.

10. The intercalated split magnet support structure according to claim 1, characterized in that: The number of tie rods is four, evenly distributed along the circumference, and the two ends are respectively connected to the fixing plate and the vacuum chamber flange by nuts.

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