A method for electron beam welding of an ellipsoidal RF superconducting cavity middle dumbbell member

Abstract

The present application relates to the field of manufacturing technology of radio frequency superconducting cavity for particle accelerator, and particularly relates to an electron beam welding method for middle dumbbell component of ellipsoidal radio frequency superconducting cavity, which uses processing tooling including beam channel main welding fixing tooling and reinforcing rib welding fixing tooling; the beam channel main welding fixing tooling includes a first elastic compensation structure, and the reinforcing rib welding fixing tooling includes a second elastic compensation structure, and the two kinds of elastic compensation structures can provide a correction force opposite to the deformation direction and positively correlated with the deformation amount in size during welding. The present application adopts the tooling with compensation structure to realize the axial compression fitting of the beam channel area and the sequential single-sided welding process of the reinforcing rib, reduces the number of tooling and the welding times, and realizes the real-time compensation of welding process defects by means of the first elastic compensation structure and the second elastic compensation structure, and reduces the irreversible deformation and deviation.

Description

Technical Field

[0001] This invention relates to the field of radio frequency superconducting cavity manufacturing technology for particle accelerators, and in particular to an electron beam welding method for the dumbbell component in the middle of an ellipsoidal radio frequency superconducting cavity. Background Technology

[0002] As particle accelerators develop towards higher gradients, higher duty cycles, and larger average current intensities, ellipsoidal radio frequency superconducting cavities made of high-purity niobium plates with an RRR ≥ 300 have become the mainstream accelerating elements. To obtain accelerating gradients > 30 MV / m in frequency bands such as 1.3 GHz and 648 MHz, the cavity generally adopts a "multi-unit series + intermediate dumbbell component" structure (e.g., Figure 4 As shown): Each pair of adjacent units shares a dumbbell component, with their equatorial ends welded together by electron beam welding. Reinforcing ribs are welded to the outer periphery of the dumbbell to improve mechanical rigidity and reduce micro-deformation during pulsed operation. However, the manufacturing chain for the intermediate dumbbell component has long been locked in by the "semi-ring reinforcing rib + multi-furnace welding" scheme, becoming a bottleneck process restricting the low-cost mass delivery of superconducting cavities.

[0003] The current mainstream process routes at home and abroad are divided into the following steps: ① Rib forming: 2.5mm thick niobium plate is blanked into two semi-circular pieces → rolled → butt tungsten inert gas welding → straightening → milling end face → drilling helium channel holes in pairs, finally obtaining two symmetrical "semi-ring ribs"; ② Dumbbell forming: two half-cells are first stamped and stretched, then CNC turned into the beam channel area, and then put into the furnace twice with two different welding fixtures to complete the two main welds inside and outside the beam channel; ③ Rib assembly: the two equatorial end faces of the welded dumbbell are forcibly opened by 0.3-0.5mm with the help of special pull clamps, two semi-ring ribs are inserted, and then locked with ring fastening hoops;

[0004] ④ Welding of reinforcing ribs: For the third furnace entry, first spot weld a fillet weld at an upward angle. After exiting the furnace, flip the component over and complete the second fillet weld for the fourth furnace entry; ⑤ Disassemble the tooling, straighten, chemically polish, and enter the cavity chain assembly.

[0005] The existing technology has the following technical problems and disadvantages in the above steps: Long processing chain for reinforcing ribs and low material utilization: The semi-ring scheme requires four processes: "rolling + butt welding + milling + matching drilling." Any dimensional deviation results in the scrapping of two parts, with material waste exceeding 15%; Irreversible deformation is introduced during assembly: After forcibly opening the two equatorial end faces, the curvature radius of the beam channel changes by 0.2-0.3mm, and post-weld springback causes the coaxiality of the cavity chain to be ≥0.15mm, directly reducing the acceleration gradient; Multiple welding furnace cycles and long production cycle: Two furnace cycles for the dumbbell main weld + one furnace cycle for the reinforcing rib fillet weld, totaling 3 furnace cycles per component. For 8 sets of components, a total of 24 furnace cycles are required, involving heating and cooling. The cumulative time is >120 hours, and repeated thermal cycling increases the risk of hydrogen absorption by niobium materials; there are many toolings and the switching time is long: 3 sets of independent welding tooling are required, with more than 20 types of parts. Each set takes 2 hours to disassemble and assemble. Repeated positioning errors accumulate, and a 0.2mm machining allowance is required for "shaping" after welding; the surface quality of the beam channel and ellipsoidal surface is reduced: repeated clamping causes inconsistent shrinkage direction. 0.1mm-0.2mm of indentation or bulging and eccentricity often appear in the beam channel area. Since the ellipsoidal radio frequency superconducting cavity unit has a thinner wall, its indentation or bulging is more serious, requiring an additional 30-50μm of chemical polishing, which consumes expensive niobium materials and increases the probability of surface contamination.

[0006] The aforementioned defects are coupled together, forming a manufacturing closed loop of "high cost - long cycle - low consistency". There is an urgent need for a new process and tooling that can complete "dumbbell main weld (beam channel area welding) + reinforcing rib pre-positioning" in the same furnace and reduce the number of clamping times. Summary of the Invention

[0007] Based on the above analysis, the present invention aims to provide an electron beam welding method for the dumbbell component in the middle of an ellipsoidal radio frequency superconducting cavity, in order to solve at least one of the following problems in existing reinforcing ribs: long processing time, low material utilization, multiple welding furnaces, introduction of irreversible deformation, large number of tooling, long switching time, large shape deviation in the beam channel region and radio frequency superconducting cavity unit.

[0008] On one hand, the present invention provides a welding and processing fixture for the dumbbell component in the middle of an ellipsoidal radio frequency superconducting cavity, including a main welding and fixing fixture for the beam channel and a welding and fixing fixture for the reinforcing ribs;

[0009] The beam channel main welding fixture is used for welding the two half-units of the dumbbell component in the middle of the ellipsoidal radio frequency superconducting cavity; the reinforcing rib welding fixture is used for welding the external reinforcing ribs at the connection between the two half-units.

[0010] The main welding fixture for the beam channel includes a first elastic compensation structure, which can provide a corrective force that is opposite to the deformation direction and positively correlated with the amount of deformation when welding the beam channel ends of the two half-units.

[0011] The welding fixture for the reinforcing rib includes a second elastic compensation structure, which provides a corrective force that is opposite to the direction of deformation and positively correlated with the amount of deformation during the welding of the reinforcing rib.

[0012] Preferably, the main welding fixture for the beam channel includes: a first handle, a first equatorial disk, an equatorial ring, and a first connecting rod;

[0013] The first handle, the first equatorial disk, the equatorial ring, and the ellipsoidal radio frequency superconducting cavity unit are coaxially arranged. The area between the first equatorial disk and the equatorial ring is the fixed forming area of ​​the ellipsoidal radio frequency superconducting cavity unit. The first handle and the first equatorial disk are fixedly connected. The first equatorial disk and the equatorial ring are connected by a first connecting rod to press and fix the ellipsoidal radio frequency superconducting cavity unit between the first equatorial disk and the equatorial ring.

[0014] The first equatorial disk is pressed and connected to the equatorial end of one half-unit in the ellipsoidal radio frequency superconducting cavity unit, and the equatorial ring is pressed and connected to the equatorial end of the other half-unit in the ellipsoidal radio frequency superconducting cavity unit. The beam channel ends of the two half-units are positioned and fixedly connected under the pressing action of the first connecting rod.

[0015] The first connecting rod is connected to the first equatorial disk and / or equatorial ring at one end and is provided with a first elastic compensation structure. The first elastic compensation structure can provide a corrective force that is opposite to the deformation direction and positively correlated with the deformation amount when the beam channel ends of the two half-units are welded.

[0016] Preferably, the first elastic compensation structure is a compression spring, the end of the first connecting rod is threaded, and a nut with matching pitch is fixed to the end of the first connecting rod passing through the compression spring.

[0017] Preferably, the first connecting rod is provided in multiple parts, which are symmetrically arranged with respect to the axial center of the first equatorial disk and the equatorial ring.

[0018] Preferably, the reinforcing rib welding and fixing fixture includes: a second handle, a second equatorial disk, a third equatorial disk, a central connecting rod, and a second elastic compensation structure;

[0019] The second grip, the second equatorial disk, and the third equatorial disk are coaxially arranged with the ellipsoidal radio frequency superconducting cavity unit; the second grip and the second equatorial disk are fixedly connected.

[0020] The second and third equatorial disks are disks with a central hole. The central connecting rod passes through the hollow area in the center of the second and third equatorial disks and can slide freely relative to the second and third equatorial disks.

[0021] One end of the central connecting rod is fixedly connected to the second handle, and the second end is connected to the third equatorial disk through the second elastic compensation structure. The second elastic compensation structure is used to adjust the displacement of the second end of the central connecting rod relative to the third equatorial disk and to adjust the pressure applied to the unit by the second equatorial disk and the third equatorial disk.

[0022] Preferably, the second handle is provided with an internal threaded recess, and the end of the central connecting rod connected to the second handle is provided with an external thread that matches the pitch of the internal threaded recess.

[0023] Preferably, the second elastic compensation structure is a disc with a central hole. The central connecting rod is connected to the second elastic compensation structure at one end with an external thread and a matching nut. The central connecting rod passes through the second elastic compensation structure. One end of the second elastic compensation structure contacts the nut, and the other end of the second elastic compensation structure contacts the third equatorial disc, so that the displacement of the second elastic compensation structure is limited between the nut and the third equatorial disc.

[0024] On the other hand, the present invention provides an electron beam welding method for an ellipsoidal radio frequency superconducting cavity intermediate dumbbell component, using the above-mentioned processing fixture, including:

[0025] S1: Based on the beam channel main welding fixture, a pair of half units and annular integrated reinforcing ribs are assembled and fixed to obtain an ellipsoidal radio frequency superconducting cavity unit preform;

[0026] S2: Electron beam welding is performed on the beam channel of the ellipsoidal radio frequency superconducting cavity unit preform to obtain a semi-finished ellipsoidal radio frequency superconducting cavity unit. Deformation correction during beam channel welding is achieved based on the first elastic compensation structure in the main beam channel welding fixture.

[0027] S3: After assembling and fixing the semi-finished ellipsoidal radio frequency superconducting cavity unit using a reinforcing rib welding fixture, reinforcing ribs are welded. Deformation correction during the reinforcing rib welding process is achieved based on the second elastic compensation structure in the reinforcing rib welding fixture.

[0028] Preferably, step S2 includes:

[0029] S201: Maintain the axial locking of the main beam channel welding fixture onto the preform, fix the first equatorial disk as a whole onto the rotating chuck of the electron beam welding machine, and evacuate to ≤5×10 - ³Pa;

[0030] S202: Beam channel welding is carried out in the same furnace. The main welding fixture provides the preset axial force throughout the welding process to compensate for shrinkage in real time.

[0031] S203: The reinforcing rib is positioned by spot welding on one side. The main welding fixture provides a preset axial force throughout the welding process to compensate for shrinkage in real time, thus obtaining an ellipsoidal radio frequency superconducting cavity unit semi-finished product.

[0032] Preferably, step S202 includes: adjusting the welding current and beam diameter during the welding process, and performing multi-stage welding.

[0033] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0034] 1. This invention uses "first elastic compensation structure + first connecting rod" for axial compression, which transforms radial indentation into elastic compression. This controls the maximum radial indentation of the beam channel region of the semi-finished dumbbell component in the middle of the ellipsoidal radio frequency superconducting cavity to ≤0.01mm and the ellipsoidality to ≤0.02mm, without the need for additional straightening, thus solving the problem of large welding deformation in the beam channel region.

[0035] 2. This invention uses a "central tie rod + second elastic compensation structure" for axial compression, which transforms circumferential contraction into elastic compression, greatly reducing the deformation of the beam channel region and the ellipsoidal radio frequency superconducting cavity unit during the welding of the reinforcing rib. The maximum deformation of the vertical axis of the beam channel region after welding is ≤0.01mm, and the maximum deformation of the vertical axis of the ellipsoidal radio frequency superconducting cavity unit is ≤0.03mm, thus solving the problem of large deformation during the welding of the reinforcing rib.

[0036] 3. This invention employs an axial pressing process of "first elastic compensation structure + first connecting rod" and "central tie rod + second elastic compensation structure" to cooperate with the beam channel area and the reinforcing ribs in a sequential single-sided welding process. This reduces the number of tooling and welding times. Furthermore, the first and second elastic compensation structures enable real-time compensation for welding defects, reducing irreversible deformation and deviations, minimizing waste of materials during subsequent polishing and grinding, and thus improving material utilization efficiency.

[0037] 4. This invention simplifies the number of tooling and the number of tooling changes by using a shared handle for the main welding fixture of the beam channel, the reinforcing rib welding fixture, the equatorial disk, and an integrated annular reinforcing rib. It also maintains the consistency of the welding reference for the two welding operations, greatly reducing the error caused by the reference and overcoming the defects of the prior art, such as the large number of tooling and the time-consuming switching. At the same time, the use of an integrated annular reinforcing rib greatly reduces the processing time of the reinforcing rib.

[0038] 5. This invention, within the same vacuum level and rotating platform, uses a three-level energy distribution of "low-high-medium" to complete "bottom sealing + full penetration + finishing" in a single furnace operation. The total heat input is comparable to that of existing double furnace operations. The back side is uniformly formed without undercut, eliminating the need for one heating / cooling cycle. The back side forming and surface quality directly reach the level of double welding. It achieves the effect of double welding in a single welding operation. Compared with existing technologies that require two heating and welding cycles of "outer furnace + inner furnace", this invention greatly shortens the welding time and improves welding efficiency.

[0039] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from the description and drawings, which are particularly pointed out. Attached Figure Description

[0040] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0041] Figure 1 is a schematic diagram of the ellipsoidal radio frequency superconducting cavity half-unit structure of the present invention;

[0042] Figure 2 This is a schematic diagram of the ellipsoidal radio frequency superconducting cavity unit structure of the present invention;

[0043] Figure 3 This is a schematic diagram of the structure of the ellipsoidal radio frequency superconducting cavity unit after welding reinforcing ribs according to the present invention;

[0044] Figure 4 This is a schematic diagram of the ellipsoidal radio frequency superconducting cavity structure of the present invention;

[0045] Figure 5 This is a schematic diagram of a typical ellipsoidal radio frequency superconducting cavity unit structure in existing technology;

[0046] Figure 6 This is a schematic diagram of the installation structure of the main welding fixture for the beam channel of the present invention;

[0047] Figure 7 for Figure 6 Sectional view of plane AA;

[0048] Figure 8 This is a schematic diagram of the main welding fixture installation structure for the beam channel of the present invention from another perspective.

[0049] Figure 9 This is a schematic diagram of the installation structure of the reinforcing rib welding and fixing fixture of the present invention;

[0050] Figure 10 for Figure 9 BB section view;

[0051] Figure 11 This is a schematic diagram of the reinforcing rib welding and fixing fixture installation structure from another perspective.

[0052] Figure label:

[0053] Ellipsoidal radio frequency superconducting cavity unit 1; half unit 01; equatorial end 011; beam channel end 012; annular groove 0121; annular reinforcing rib mounting part 013; reinforcing rib 02; first through hole 021; first equatorial disk 03a; equatorial ring 04; first connecting rod 05; first handle 06a; groove 061; first elastic compensation structure 07; second handle 06b; second equatorial disk 03b; third equatorial disk 08; central connecting rod 09; second elastic compensation structure 10; nut 11. Detailed Implementation

[0054] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0055] In a first aspect, the present invention discloses an ellipsoidal radio frequency superconducting cavity intermediate dumbbell component, such as... Figures 1-4 As shown, it includes: multiple ellipsoidal radio frequency superconducting cavity units that are sequentially connected axially in an ellipsoidal radio frequency superconducting cavity;

[0056] Each ellipsoidal radio frequency superconducting cavity unit contains two half-units and reinforcing ribs;

[0057] The semi-unit is a semi-ellipsoidal hollow chamber with two opposing open ends, the larger open end being the equatorial end and the smaller open end being the beam channel end;

[0058] The outer periphery of the beam channel end is provided with an annular reinforcing rib mounting part. The beam channel ends of the two half-units are fixedly connected, and the reinforcing rib mounting parts on the outer periphery of the beam channel ends of the two half-units are fixedly connected by the reinforcing ribs.

[0059] Preferably, the ends of the beam channel of the two half-units in the same unit are provided with a retaining structure, which enables the beam channel ends of the two half-units to be accurately engaged.

[0060] Specifically, the beam channel end of one half-unit in the same unit is provided with an annular groove, and the beam channel end of the other half-unit can be matched and embedded into the annular groove to achieve accurate positioning.

[0061] Preferably, the reinforcing rib is an integral ring structure with a first through hole on its surface; the first through hole serves as a refrigerant channel and a vacuum pumping channel, ensuring that the refrigerant can quickly enter and exit the slit between the reinforcing rib and the cavity wall during cavity operation and to quickly pump a vacuum from the slit between the reinforcing rib and the cavity wall.

[0062] It should be noted that, as Figure 5As shown, since the welding process of the beam channel end in the prior art involves two welding processes, one inside and one outside, the integrated circular structure reinforcing rib will block the external welding of the beam channel end. Therefore, the reinforcing rib in the prior art is formed by welding two semi-circular rings together.

[0063] Secondly, this invention discloses a welding fixture for the dumbbell-shaped intermediate component of an ellipsoidal radio frequency superconducting cavity, such as... Figures 6-11 As shown, it includes the main welding fixture for the beam channel and the welding fixture for the reinforcing ribs;

[0064] The beam channel main welding fixture is used for welding the two half-units of the dumbbell component in the middle of the ellipsoidal radio frequency superconducting cavity, and the reinforcing rib welding fixture is used for welding the external reinforcing ribs at the connection between the two half-units.

[0065] The main welding fixture for the beam channel includes a first elastic compensation structure, which can provide a corrective force that is opposite to the deformation direction and positively correlated with the amount of deformation when welding the beam channel ends of the two half-units.

[0066] The welding fixture for reinforcing ribs includes a second elastic compensation structure, which provides a corrective force that is opposite to the direction of deformation and positively correlated with the amount of deformation during the welding of the reinforcing ribs.

[0067] Specifically, the main welding fixture for the beam channel includes:

[0068] First grip, first equatorial disc, equatorial ring, first connecting rod;

[0069] The first handle, the first equatorial disk, the equatorial ring, and the ellipsoidal radio frequency superconducting cavity unit are coaxially arranged. The area between the first equatorial disk and the equatorial ring is the fixed forming area of ​​the ellipsoidal radio frequency superconducting cavity unit. The first handle and the first equatorial disk are fixedly connected. The first equatorial disk and the equatorial ring are connected by a first connecting rod to press and fix the ellipsoidal radio frequency superconducting cavity unit between the first equatorial disk and the equatorial ring.

[0070] The first equatorial disk is pressed and connected to the equatorial end of one half-unit in the ellipsoidal radio frequency superconducting cavity unit, and the equatorial ring is pressed and connected to the equatorial end of the other half-unit in the ellipsoidal radio frequency superconducting cavity unit. The beam channel ends of the two half-units are positioned and fixedly connected under the pressing action of the first connecting rod.

[0071] The first connecting rod is connected to the first equatorial disk and / or equatorial ring at one end, and is provided with a first elastic compensation structure. The first elastic compensation structure can provide a corrective force that is opposite to the deformation direction and positively correlated with the deformation amount when the beam channel ends of the two half-units are welded, suppressing the deformation and correcting the deformation that has already occurred, thereby greatly reducing the amount of deformation.

[0072] It should be noted that in the existing technology, when adjacent half-units are butt-welded at the beam channel end, local instability occurs due to "thermal-mechanical coupling," resulting in millimeter-level deformation: the localization of the heat source causes a sharp drop in the elastic modulus, which is insufficient to maintain its own structure under internal and external stresses → the temperature gradient between the radial molten pool center and the edge is steep, and thermal compressive stress is generated due to the difference in thermal expansion → the thin wall at the beam channel end collapses inward under the action of thermal compressive stress, forming a radial indentation of 0.05mm~0.10mm.

[0073] Specifically, the first elastic compensation structure can be a compression spring, the end of the first connecting rod is threaded, and the end of the first connecting rod passes through the compression spring and is fixed with a nut of matching pitch. The nut fixes the compression spring between the first equatorial disk and / or the equatorial ring.

[0074] During implementation, before welding, the pressure springs in different areas are adjusted to compress and deform, and a uniform compressive force is applied to the first equatorial disk and / or equatorial ring. The first equatorial disk and equatorial ring apply opposing pressures to both ends of the ellipsoidal radio frequency superconducting cavity unit. When welding deformation occurs, the pressure springs corresponding to the deformed areas are displaced under the deformation action, and the compressive force applied to the deformed areas changes. The change in compressive force serves as a corrective force to correct the deformation of the deformed areas, thereby reducing or eliminating the deformation.

[0075] Compared with the prior art, the present invention adopts "first elastic compensation structure + first connecting rod" for axial compression, which transforms radial indentation into elastic compression. This controls the maximum radial indentation of the beam channel region of the semi-finished dumbbell component in the middle of the ellipsoidal radio frequency superconducting cavity to ≤0.01mm and ellipsoidality to ≤0.02mm, without the need for additional straightening, thus solving the problem of large welding deformation in the beam channel region.

[0076] Preferably, there are multiple first connecting rods, which are symmetrically arranged relative to the axial center of the first equatorial disk and the equatorial ring.

[0077] Specifically, the edge of the first equatorial disk is provided with a plurality of first through holes, which are symmetrically arranged with respect to the central axis of the first equatorial disk; the edge of the equatorial ring is provided with a plurality of second through holes, which are symmetrically arranged with respect to the central axis of the equatorial ring and corresponding to the first through holes, so that a first connecting rod can pass through a set of corresponding first through holes and second through holes at the same time.

[0078] In practice, multiple first connecting rods, first through holes, and second through holes are provided and are symmetrically arranged relative to the axis center of the first equatorial disk and the equatorial ring, which can achieve uniform pressing when adjacent half units are docked and welded at the beam channel end.

[0079] Specifically, a flange is provided at one end of the first handle that is fixedly connected to the first equatorial disk, and the first handle is fixedly connected to the first equatorial disk through the flange.

[0080] Preferably, the first equatorial disk and the equatorial ring are provided with an annular groove, which matches the equatorial end of the half-unit, so that the equatorial end can be engaged inside the annular groove.

[0081] Specifically, the welding and fixing fixture for the reinforcing ribs includes:

[0082] Second grip, second equatorial disc, third equatorial disc, central connecting rod, and second elastic compensation structure;

[0083] The second grip, the second equatorial disk, and the third equatorial disk are coaxially arranged with the ellipsoidal radio frequency superconducting cavity unit; the second grip and the second equatorial disk are fixedly connected.

[0084] The second and third equatorial disks are disks with a central hole. The central connecting rod passes through the hollow area in the center of the second and third equatorial disks and can slide freely relative to the second and third equatorial disks.

[0085] One end of the central connecting rod is fixedly connected to the second handle, and the second end is connected to the third equatorial disk through the second elastic compensation structure. The second elastic compensation structure is used to adjust the displacement of the second end of the central connecting rod relative to the third equatorial disk and to adjust the pressure applied to the unit by the second equatorial disk and the third equatorial disk.

[0086] During implementation, the second elastic compensation structure is adjusted to a compressed state. The second elastic compensation structure provides compressive forces in opposite directions to the third equatorial disk and the central connecting rod. Since the central connecting rod is fixedly connected to the second handle and the second equatorial disk, the compressive force provided by the second elastic compensation structure to the third equatorial disk and the central connecting rod realizes the compression of the ellipsoidal radio frequency superconducting cavity unit by the second equatorial disk and the third equatorial disk. During the welding of the reinforcing ribs, the circumferential contraction is converted into elastic compression, and the displacement is compensated in real time, reducing or basically eliminating the above deformation.

[0087] It should be noted that during the welding of the reinforcing ribs, the heat is concentrated in the thin-walled region on the outer equator, resulting in the following deformation:

[0088] Outer diameter deformation: The heat-affected zone (approximately 4 mm wide) experiences instantaneous temperature rise → decreases elastic modulus → is subjected to circumferential tension, and generates circumferential contraction stress after cooling, causing the outer diameter of the welded joint of the ellipsoidal radio frequency superconducting cavity unit to increase by 0.05 mm–0.08 mm, forming a "bulge".

[0089] Corner collapse: The thickness of the reinforcing rib can reach 2.5mm, the penetration depth of the fillet weld can reach 2mm, and the metal in the near-weld area collapses inward by 0.02mm–0.03mm, causing a local "V" shaped notch and increasing stress concentration.

[0090] Axial warping: The contraction force is transmitted to the equatorial end of the dumbbell through the reinforcing rib, causing a slight outward warping of 0.01mm–0.02mm in the beam channel area. Although this is less than the deformation of the main weld of the beam channel, it still affects the coaxiality of the cavity chain after being superimposed.

[0091] Compared with the prior art, the present invention adopts "central tie rod + second elastic compensation structure" for axial compression, which transforms circumferential contraction into elastic compression, greatly reducing the deformation of the beam channel region and the ellipsoidal radio frequency superconducting cavity unit during the welding of the reinforcing rib. The maximum deformation of the vertical axis of the beam channel region after welding is ≤0.01mm, and the maximum deformation of the ellipsoidal radio frequency superconducting cavity unit is ≤0.03mm, thus solving the problem of large deformation during the welding of the reinforcing rib.

[0092] Specifically, the second handle is provided with an internal threaded recess, and the end of the central connecting rod connected to the second handle is provided with an external thread that matches the pitch of the internal threaded recess.

[0093] Specifically, the second elastic compensation structure has a central hole, and the central connecting rod is connected to the second elastic compensation structure at one end with an external thread and a matching nut. The central connecting rod passes through the second elastic compensation structure, one end of the second elastic compensation structure contacts the nut, and the other end of the second elastic compensation structure contacts the third equatorial disk, so that the displacement of the second elastic compensation structure is limited between the nut and the third equatorial disk.

[0094] Specifically, the second elastic compensation structure can be a spring.

[0095] Preferably, the first equatorial disk and the third equatorial disk are also provided with ventilation holes for heat dissipation from the inside of the ellipsoidal radio frequency superconducting cavity unit to the outside during the welding process.

[0096] Preferably, the third equatorial disk is provided with an annular groove, which matches the equatorial end of the half-unit, so that the equatorial end can be engaged inside the annular groove.

[0097] Preferably, the first equatorial disk and the second equatorial disk are the same, and the first handle and the second handle are the same. Changing the welding fixture only requires changing the fixing fixture on the other side of the ellipsoidal radio frequency superconducting cavity unit, which simplifies the number of fixtures and the number of times to change them.

[0098] Fourthly, this invention discloses an electron beam welding method for an ellipsoidal radio frequency superconducting cavity intermediate dumbbell component, using the aforementioned beam channel main welding fixture and reinforcing rib welding fixture, comprising:

[0099] S1: Based on the beam channel main welding fixture, a pair of half units and annular integrated reinforcing ribs are assembled and fixed to obtain an ellipsoidal radio frequency superconducting cavity unit preform;

[0100] S2: Electron beam welding is performed on the beam channel of the ellipsoidal radio frequency superconducting cavity unit preform to obtain a semi-finished ellipsoidal radio frequency superconducting cavity unit. Deformation correction during beam channel welding is achieved based on the first elastic compensation structure in the main beam channel welding fixture.

[0101] S3: After assembling and fixing the semi-finished ellipsoidal radio frequency superconducting cavity unit using a reinforcing rib welding fixture, reinforcing ribs are welded. Deformation correction during the reinforcing rib welding process is achieved based on the second elastic compensation structure in the reinforcing rib welding fixture.

[0102] During implementation, the first and second grips of the main beam channel welding fixture and the reinforcing rib welding fixture are the same, as are the first and second equatorial disks. Subsequently, only the other side of the ellipsoidal radio frequency superconducting cavity unit needs to be replaced, which simplifies the number of fixtures and the number of replacements, and maintains the same welding reference for the two times, greatly reducing the error caused by the reference. Furthermore, the use of annular integrated reinforcing ribs avoids the use of reinforcing rib fixing fixtures, further simplifying the number of fixtures and the number of replacements.

[0103] Compared with the prior art, the present invention adopts the axial pressing of "first elastic compensation structure + first connecting rod" and "central tie rod + second elastic compensation structure" in combination with the beam channel area and the reinforcing rib sequential single-sided welding process, which reduces the number of tooling and welding times. Furthermore, the first elastic compensation structure and the second elastic compensation structure enable real-time compensation of welding process defects, reducing irreversible deformation and deviation.

[0104] Compared with the prior art, the present invention simplifies the number of tooling and the number of tooling changes by using a common handle for the main welding fixture of the beam channel, the reinforcing rib welding fixture, the equatorial disk, and the use of annular integrated reinforcing ribs. It also maintains the consistency of the welding reference for the two welding processes, greatly reducing the error caused by the reference and overcoming the defects of the prior art in terms of the large number of tooling and the time-consuming switching. At the same time, the use of annular integrated reinforcing ribs greatly reduces the processing time of the reinforcing ribs.

[0105] Specifically, step S1 includes:

[0106] S101: Press the equatorial end of one and a half units into the annular groove of the first equatorial disk of the main welding fixture for the beam channel, so that the beam channel end is exposed.

[0107] S102: The annular integral reinforcing rib is axially slidably sleeved outside the half-unit beam channel end that has been fixed in step S101. The inner diameter of the reinforcing rib can slide and fit with the beam channel end without expansion.

[0108] S103: Align the beam channel of the second half-unit with the annular groove of the beam channel of the half-unit fixed in step S101 and insert it into the groove. At the same time, press the equatorial end of the second half-unit into the corresponding annular groove of the equatorial ring to form a coaxial dumbbell-reinforcing rib assembly.

[0109] S104: Simultaneously tighten the nuts at both ends of the first connecting rod to compress the first elastic compensation structure, generating an axial force of 3kN~5kN, so that the two halves of the unit and the reinforcing rib are axially pressed together to obtain an ellipsoidal radio frequency superconducting cavity unit preform.

[0110] Specifically, step S2 includes:

[0111] S201: Maintain the axial locking of the main beam channel welding fixture onto the preform, fix the first equatorial disk as a whole onto the rotating chuck of the electron beam welding machine, and evacuate to ≤5×10 - ³Pa;

[0112] S202: Beam channel welding is carried out in the same furnace. The main welding fixture provides 3kN~5kN axial force throughout the welding process to compensate for shrinkage in real time.

[0113] S203: The reinforcing rib is positioned by spot welding on one side. The main welding fixture provides 3kN~5kN axial force throughout the welding process to compensate for shrinkage in real time, thus obtaining an ellipsoidal radio frequency superconducting cavity unit semi-finished product.

[0114] Preferably, step S202 includes: adjusting the welding current and beam diameter during the welding process, and performing multi-stage welding.

[0115] Specifically, step S202 includes:

[0116] S2021: Pre-sealing welding is performed using a voltage of 140KV~160KV, a current of 14.5mA~15.5mA, a welding rotation speed of 7mm / s~9mm / s, and a beam diameter of 3.8mm~4.5mm.

[0117] S2022: Through welding is performed using a voltage of 140KV~160KV, a current of 18.5mA~19.5mA, a welding rotation speed of 7mm / s~9mm / s, and a beam diameter of 3.8mm~4.5mm.

[0118] S2023: Modification welding is performed using a voltage of 140KV~160KV, a current of 15.8mA~16.5mA, a welding rotation speed of 7mm / s~9mm / s, and a beam diameter of 5.5mm~6.5mm.

[0119] It should be noted that pre-sealing welding can quickly seal the gap at the root of the beam channel, preventing back-side leakage or depression during subsequent deep melting; it is equivalent to the "inner seam" function of existing technology, but without the need to flip the furnace or reverse welding; through welding penetrates the wall thickness in one go and forms a certain back-side reinforcement, achieving the penetration depth index of the "outer seam" of existing technology; at the same time, because of pre-sealing welding, the root of the beam channel has been pre-sealed, and the back-side is uniformly formed without undercut; finishing welding can widen the beam and smooth the molten pool, eliminate undercut and reinforcement protrusion, and reduce the need for subsequent 30µm chemical polishing.

[0120] Compared with existing technologies, this invention uses a three-level energy distribution of "low-high-medium" within the same vacuum level and rotating platform to complete "bottom sealing + full penetration + finishing" in a single furnace operation. The total heat input is comparable to that of existing double furnace operations. The back side is uniformly formed without undercut, eliminating the need for one heating / cooling time. The back side forming and surface quality directly reach the level of double welding. It achieves the effect of double welding in a single welding operation, which greatly shortens the welding time and improves welding efficiency compared to existing technologies that require two heating and welding operations: "outer furnace + inner furnace".

[0121] Specifically, step S203 includes:

[0122] Spot welding positioning is performed using a voltage of 50KV~70KV, a current of 160mA~190mA, a welding rotation speed of 23mm / s~28mm / s, and a beam diameter of 20mm~30mm.

[0123] It should be noted that the voltage of 50kV~70kV and the current of 160mA~190mA ensure that the already welded beam channel is not damaged; the welding rotation speed of 23mm / s~28mm / s ensures a short dwell time, allowing the weld pool to solidify quickly and avoiding secondary shrinkage of the beam channel welding area caused by the entire beam channel heating up; the beam spot diameter of 20mm~30mm allows the bevels on the rib side and dumbbell side to be melted simultaneously in one scan, eliminating the need for oscillation and reducing thermal interference to the beam channel.

[0124] Specifically, step S3 includes:

[0125] S301: After completing the beam channel welding, remove the equatorial ring and connecting rod of the main beam channel welding fixture, retain the first handle and the first equatorial disk as positioning references, and snap the third equatorial disk into place on the other side of the ellipsoidal radio frequency superconducting cavity unit semi-finished product away from the first handle. Pass the central connecting rod through the third equatorial disk, fix the ellipsoidal radio frequency superconducting cavity unit semi-finished product and the first handle, and at the end of the central connecting rod that passes through the third equatorial disk, install the gasket, the second elastic compensation structure and the nut in sequence, and tighten the nuts symmetrically to make the ellipsoidal radio frequency superconducting cavity unit semi-finished product and the third equatorial disk fastened together.

[0126] S302: Keep the same handle engaged in the electron beam welding machine's rotary chuck, set the elevation angle to 25°~35°, and evacuate to a vacuum level of ≤5×10⁻⁶. -3 Pa;

[0127] S303: Set the electron beam parameters: voltage 60kV~80kV, current 250mA~350mA, welding rotation speed 10mm / s~15mm / s, beam spot diameter 4mm~6mm. First, bombard the unwelded fillet weld on the side of the reinforcing rib, and then rotate continuously for one revolution to complete the full penetration welding of the fillet weld on the other side of the reinforcing rib.

[0128] Specifically, in step S301, after tightening the nut, the second elastic compensation structure is compressed by 3mm to 5mm, forming an axial preload of 8kN to 12kN.

[0129] It should be noted that a compression of 3mm to 5mm keeps the spring in its optimal elastic range, which avoids both complete compression and loss of compensation ability, and prevents excessive stroke leading to insufficient preload. The preload of 8kN to 12kN is always greater than the contraction force, forming an interference compensation margin to ensure that the outer diameter of the reinforcing rib does not bulge after welding and that the ellipsoid is controllable.

[0130] To better illustrate the present invention, the following embodiments and comparative examples are further provided:

[0131] Example 1

[0132] This embodiment discloses a welding fixture for the dumbbell-shaped intermediate component of an ellipsoidal radio frequency superconducting cavity, such as... Figures 6-11 As shown, it includes the main welding fixture for the beam channel and the welding fixture for the reinforcing ribs.

[0133] The main welding fixture for the beam channel includes:

[0134] First grip, first equatorial disc, equatorial ring, first connecting rod;

[0135] The first handle, the first equatorial disk, the equatorial ring, and the ellipsoidal radio frequency superconducting cavity unit are coaxially arranged. The area between the first equatorial disk and the equatorial ring is the fixed forming area of ​​the ellipsoidal radio frequency superconducting cavity unit. The first handle and the first equatorial disk are fixedly connected. The first equatorial disk and the equatorial ring are connected by a first connecting rod to press and fix the ellipsoidal radio frequency superconducting cavity unit between the first equatorial disk and the equatorial ring.

[0136] The first equatorial disk is pressed and connected to the equatorial end of one half-unit in the ellipsoidal radio frequency superconducting cavity unit, and the equatorial ring is pressed and connected to the equatorial end of the other half-unit in the ellipsoidal radio frequency superconducting cavity unit. The beam channel ends of the two half-units are positioned and fixedly connected under the pressing action of the first connecting rod.

[0137] The first connecting rod is connected to the first equatorial disk at one end with a first elastic compensation structure. The first elastic compensation structure can provide a corrective force that is opposite to the deformation direction and positively correlated with the deformation amount when the beam channel ends of the two half-units are welded, suppressing deformation and correcting the deformation that has already occurred, thus greatly reducing the amount of deformation.

[0138] The first elastic compensation structure is a compression spring. The end of the first connecting rod is threaded. After the first connecting rod passes through the compression spring, the end is fixed with a nut with a matching pitch. The nut fixes the compression spring between the nut and the first equatorial disk.

[0139] Before welding, the pressure springs in different areas are adjusted to compress and deform, and a uniform compressive force is applied to the first equatorial disk and / or the equatorial ring. The first equatorial disk and the equatorial ring apply opposing pressures to both ends of the ellipsoidal radio frequency superconducting cavity unit. When welding deformation occurs, the pressure springs corresponding to the deformed areas are displaced under the action of deformation, and the compressive force applied to the deformed areas changes. The change in compressive force is used as a corrective force to correct the deformation of the deformed areas, so that the deformation is reduced or eliminated.

[0140] There are four first connecting rods, which are symmetrically arranged with respect to the axis center of the first equatorial disk and the equatorial ring.

[0141] The edge of the first equatorial disk has a first through hole, which is symmetrically arranged with respect to the axis of the first equatorial disk; the edge of the equatorial ring has four second through holes, which are symmetrically arranged with respect to the axis of the equatorial ring and corresponding to the first through holes, so that a first connecting rod can pass through a set of corresponding first and second through holes at the same time.

[0142] The first connecting rod, the first through hole, and the second through hole are provided in four parts, and are symmetrically arranged relative to the axis center of the first equatorial disk and the equatorial ring, which can realize uniform pressing when adjacent half units are docked and welded at the beam channel end.

[0143] The first handle is fixedly connected to the first equatorial disk at one end, and a flange is provided at the other end. The first handle is fixedly connected to the first equatorial disk through the flange.

[0144] The first equatorial disk and equatorial ring are provided with annular grooves. The annular grooves match the equatorial ends of the half-units, allowing the equatorial ends to engage inside the annular grooves.

[0145] The welding and fixing fixture for reinforcing ribs includes:

[0146] Second grip, first equatorial disc, third equatorial disc, central connecting rod, and second elastic compensation structure;

[0147] The second grip, the first equatorial disk, the third equatorial disk, and the ellipsoidal radio frequency superconducting cavity unit are coaxially arranged; the second grip and the first equatorial disk are fixedly connected.

[0148] The first and third equatorial disks are disks with a central hole. The central connecting rod passes through the hollow area in the center of the first and third equatorial disks and can slide freely relative to the first and third equatorial disks.

[0149] One end of the central connecting rod is fixedly connected to the second handle, and the second end is connected to the third equatorial disk through the second elastic compensation structure. The second elastic compensation structure is used to adjust the displacement of the second end of the central connecting rod relative to the third equatorial disk and to adjust the pressure applied to the unit by the first equatorial disk and the third equatorial disk.

[0150] The second elastic compensation structure is adjusted to a compressed state, and the second elastic compensation structure provides a compressive force in opposite directions to the third equatorial disk and the central connecting rod. Since the central connecting rod is fixedly connected to the second handle and the first equatorial disk, the compressive force provided by the second elastic compensation structure to the third equatorial disk and the central connecting rod realizes the compression of the ellipsoidal radio frequency superconducting cavity unit by the first equatorial disk and the third equatorial disk. During the welding of the reinforcing rib, the circumferential contraction is converted into elastic compression, and the displacement is compensated in real time, reducing or basically eliminating the above deformation.

[0151] The second elastic compensation structure has a central hole. The central connecting rod is connected to the second elastic compensation structure at one end with an external thread and a matching nut. The central connecting rod passes through the second elastic compensation structure. One end of the second elastic compensation structure contacts the nut, and the other end of the second elastic compensation structure contacts the third equatorial disk, so that the displacement of the second elastic compensation structure is limited between the nut and the third equatorial disk.

[0152] The second elastic compensation structure is a spring.

[0153] The first and third equatorial disks are also equipped with ventilation holes for heat dissipation from the inside of the ellipsoidal radio frequency superconducting cavity unit to the outside during the welding process.

[0154] The third equatorial disk is provided with an annular groove, which matches the equatorial end of the half-unit, allowing the equatorial end to engage inside the annular groove.

[0155] Example 2

[0156] This embodiment discloses an electron beam welding method for the intermediate dumbbell component of an ellipsoidal radio frequency superconducting cavity, such as... Figures 6-11 As shown, using the machining fixture of Example 1, a dumbbell component with a semi-unit size of 50mm major axis and 30mm minor axis, and a reinforcing rib thickness of 2.5mm is machined, including:

[0157] S1: Based on the beam channel main welding fixture, a pair of half-units and annular integrated reinforcing ribs are assembled and fixed to obtain an ellipsoidal radio frequency superconducting cavity unit preform, including:

[0158] S101: Press the equatorial end of one and a half units into the annular groove of the first equatorial disk of the main welding fixture for the beam channel, so that the beam channel end is exposed.

[0159] S102: The annular integral reinforcing rib is axially slidably sleeved outside the half-unit beam channel end that has been fixed in step S101. The inner diameter of the reinforcing rib can slide and fit with the beam channel end without expansion.

[0160] S103: Align the beam channel of the second half-unit with the annular groove of the beam channel of the half-unit fixed in step S101 and insert it into the groove. At the same time, press the equatorial end of the second half-unit into the corresponding annular groove of the equatorial ring to form a coaxial dumbbell-reinforcing rib assembly.

[0161] S104: Simultaneously tighten the nuts at both ends of the first connecting rod to compress the first elastic compensation structure, generating a 4kN axial force, so that the two halves of the unit and the reinforcing rib are axially pressed together to obtain an ellipsoidal radio frequency superconducting cavity unit preform.

[0162] S2: Electron beam welding is performed on the beam channel of the ellipsoidal radio frequency superconducting cavity unit preform to obtain a semi-finished ellipsoidal radio frequency superconducting cavity unit. Deformation correction during beam channel welding is achieved based on the first elastic compensation structure in the main beam channel welding fixture, including:

[0163] S201: Maintain the axial locking of the main beam channel welding fixture onto the preform, fix the first equatorial disk as a whole onto the rotating chuck of the electron beam welding machine, and evacuate to ≤5×10 - ³Pa;

[0164] S202: Beam channel welding is performed within the same heat cycle. The entire welding process is supported by a 4kN axial force provided by the main welding fixture, with real-time compensation for shrinkage, including:

[0165] S2021: Pre-sealing welding is performed using a voltage of 150KV, a current of 15mA, a welding rotation speed of 8mm / s, and a beam diameter of 4mm.

[0166] S2022: Through welding is performed using a voltage of 150KV, a current of 19mA, a welding rotation speed of 8mm / s, and a beam diameter of 4mm.

[0167] S2023: Modification welding is performed using a voltage of 150KV, a current of 16mA, a welding rotation speed of 8mm / s, and a beam diameter of 6mm.

[0168] S203: Spot welding is used to position the reinforcing rib on one side. The main welding fixture provides 4kN axial force throughout the welding process to compensate for shrinkage in real time, resulting in an ellipsoidal radio frequency superconducting cavity unit semi-finished product. Spot welding is performed using a voltage of 60KV, a current of 170mA, a welding rotation speed of 26mm / s, and a beam spot diameter of 25mm.

[0169] S3: After assembling and fixing the semi-finished ellipsoidal radio frequency superconducting cavity unit using a reinforcing rib welding fixture, reinforcing ribs are welded. Deformation correction during the reinforcing rib welding process is achieved based on the second elastic compensation structure in the reinforcing rib welding fixture, including:

[0170] S301: After completing the beam channel welding, remove the equatorial ring and connecting rod of the main beam channel welding fixture, retaining the first handle and the first equatorial disk as positioning references. Secure the third equatorial disk as a whole to the other side of the ellipsoidal RF superconducting cavity unit semi-finished product away from the first handle. Pass the central connecting rod through the third equatorial disk, fix the ellipsoidal RF superconducting cavity unit semi-finished product to the first handle, and at the end of the central connecting rod that protrudes from the third equatorial disk, install the gasket, the second elastic compensation structure, and the nut in sequence. Tighten the nuts symmetrically to make the ellipsoidal RF superconducting cavity unit semi-finished product and the third equatorial disk firmly integrated. After tightening the nuts, the second elastic compensation structure is compressed by 4mm, forming an axial preload of 10kN.

[0171] S302: Keep the same handle engaged in the electron beam welding machine's rotary chuck, set the elevation angle to 30°, and evacuate to ≤5×10⁻⁶. - 3 Pa;

[0172] S303: Set the electron beam parameters: voltage 70kV, current 300mA, welding rotation speed 12mm / s, beam spot diameter 5mm. First, bombard the unwelded fillet weld on the side of the reinforcing rib, then rotate continuously for one revolution to complete the full penetration welding of the fillet weld on the other side of the reinforcing rib.

[0173] Example 3

[0174] This embodiment discloses an electron beam welding method for the intermediate dumbbell component of an ellipsoidal radio frequency superconducting cavity, such as... Figure 1 As shown, the main beam channel welding fixture of Example 1 and the reinforcing rib welding fixture of Example 2 were used, with adaptive adjustments to the dimensions. A dumbbell component with a semi-unit size of 90mm major axis and 60mm minor axis was machined, and the reinforcing rib thickness was 4.5mm. The difference from Example 2 is as follows:

[0175] S202: Beam channel welding is performed within the same heat cycle. The entire welding process is supported by a 4kN axial force provided by the main welding fixture, with real-time compensation for shrinkage, including:

[0176] S2021: Pre-sealing welding is performed using a voltage of 160KV, a current of 15mA, a welding rotation speed of 8mm / s, and a beam diameter of 4mm.

[0177] S2022: Through welding is performed using a voltage of 160KV, a current of 20mA, a welding rotation speed of 9mm / s, and a beam diameter of 4mm.

[0178] S2023: Modification welding is performed using a voltage of 160KV, a current of 16mA, a welding rotation speed of 9mm / s, and a beam diameter of 6mm.

[0179] S203: Spot welding is used to position the reinforcing rib on one side. The main welding fixture provides 5kN axial force throughout the welding process to compensate for shrinkage in real time, resulting in an ellipsoidal radio frequency superconducting cavity unit semi-finished product. Spot welding is performed using a voltage of 70KV, a current of 180mA, a welding rotational linear speed of 26mm / s, and a beam spot diameter of 25mm.

[0180] S303: Set the electron beam parameters: voltage 80kV, current 300mA, welding rotation speed 13mm / s, beam spot diameter 6mm. First, bombard the unwelded fillet weld on the side of the reinforcing rib, then rotate continuously for one revolution to complete the full penetration welding of the fillet weld on the other side of the reinforcing rib.

[0181] Comparative Example 1

[0182] This comparative example provides an electron beam welding method for the dumbbell-shaped intermediate component of an ellipsoidal radio frequency superconducting cavity, which differs from Example 2 in that:

[0183] S202: Beam channel welding is carried out in the same furnace. The main welding fixture provides 4kN axial force throughout the welding process to compensate for shrinkage in real time. The welding process is set with a stable voltage of 150KV, a current of 19mA, a welding rotation speed of 8mm / s, and a beam spot diameter of 4mm for through welding. The rest is the same as in Example 2.

[0184] Comparative Example 2

[0185] This comparative example describes an electron beam welding method for the dumbbell-shaped intermediate component of an ellipsoidal radio frequency superconducting cavity. The difference between this example and Example 2 is that the main welding fixture for the beam channel without a first elastic compensation structure is used. Otherwise, the method is the same as Example 2.

[0186] Comparative Example 3

[0187] This comparative example describes an electron beam welding method for the dumbbell-shaped intermediate component of an ellipsoidal radio frequency superconducting cavity. The difference between this example and Example 2 is that a welding fixture without a second elastic compensation structure is used for fixing the reinforcing ribs. Otherwise, the method is the same as Example 2.

[0188] The test results of the dumbbell-shaped intermediate component of the ellipsoidal radio frequency superconducting cavity in the examples and comparative examples are as follows:

[0189]

[0190] It should be noted that the maximum radial indentation refers to the maximum radial collapse of the channel's thin wall towards the inner side of the cavity caused by thermal shrinkage instability. Measurement methods include:

[0191] Using the theoretical circle of the beam channel region after welding as a reference, take 3 points (3 points in total) on each of the four generatrices at 0°, 90°, 180° and 270° using a coordinate measuring machine (CMM) or an inside micrometer. Read the maximum negative deviation between the actual radius and the theoretical radius, which is the maximum radial indentation of the cross section. Take the maximum negative deviation among all cross sections as the final result of the component with an accuracy of 0.001mm.

[0192] Ellipsoid refers to the difference between the maximum and minimum outer diameters of the circular cross-section of the beam channel region, which can be obtained by measuring the outer diameter using a coordinate measuring machine (CMM).

[0193] The maximum deformation of the vertical axis of the beam channel region and the maximum deformation of the vertical axis of the ellipsoidal radio frequency superconducting cavity unit can also be measured using a coordinate measuring machine (CMM). Three points (a total of 12 points) are taken on each of the four generatrices (0°, 90°, 180°, and 270°) of the beam channel region and the ellipsoidal radio frequency superconducting cavity unit. The distances between the outer and inner wall coordinates and the axis of the beam channel region are calculated, and the maximum distance is recorded as the maximum deformation of the vertical axis of the beam channel region. Similarly, the distances between the outer and inner wall coordinates and the axis of the ellipsoidal radio frequency superconducting cavity unit are calculated, and the maximum distance is recorded as the maximum deformation of the vertical axis of the ellipsoidal radio frequency superconducting cavity unit.

[0194] The results show that the maximum radial indentation of the beam channel region of the semi-finished ellipsoidal radio frequency superconducting cavity intermediate dumbbell component prepared in the embodiments of the present invention is controlled within ≤0.01mm and the ellipsoidality is ≤0.02mm, requiring no additional correction; the maximum deformation of the vertical axis of the beam channel region of the finished ellipsoidal radio frequency superconducting cavity intermediate dumbbell component prepared in the embodiments of the present invention is ≤0.01mm, and the maximum deformation of the vertical axis of the ellipsoidal radio frequency superconducting cavity unit is ≤0.03mm.

[0195] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for electron beam welding of a dumbbell-shaped intermediate component in an ellipsoidal radio frequency superconducting cavity, characterized in that, Use beam channel main welding fixture and reinforcing rib welding fixture; The beam channel main welding fixture is used for welding the two half-units of the dumbbell component in the middle of the ellipsoidal radio frequency superconducting cavity; the reinforcing rib welding fixture is used for welding the external reinforcing rib at the connection between the two half-units. The main welding fixture for the beam channel includes a first elastic compensation structure, which can provide a corrective force that is opposite to the deformation direction and positively correlated with the amount of deformation when welding the beam channel ends of the two half-units. The welding fixture for the reinforcing rib includes a second elastic compensation structure, which can provide a corrective force that is opposite to the deformation direction and positively correlated with the amount of deformation during the welding of the reinforcing rib. The electron beam welding method for the dumbbell-shaped intermediate component of the ellipsoidal radio frequency superconducting cavity includes: S1: Based on the beam channel main welding fixture, a pair of half units and annular integrated reinforcing ribs are assembled and fixed to obtain an ellipsoidal radio frequency superconducting cavity unit preform; S2: Electron beam welding is performed on the beam channel of the ellipsoidal radio frequency superconducting cavity unit preform to obtain a semi-finished ellipsoidal radio frequency superconducting cavity unit. Deformation correction during beam channel welding is achieved based on the first elastic compensation structure in the main beam channel welding fixture. S3: After assembling and fixing the semi-finished ellipsoidal radio frequency superconducting cavity unit using a reinforcing rib welding fixture, reinforcing ribs are welded. Deformation correction during the reinforcing rib welding process is achieved based on the second elastic compensation structure in the reinforcing rib welding fixture. Step S2 includes: S201: Maintain the axial locking of the main beam channel welding fixture onto the preform, fix the first equatorial disk as a whole onto the rotating chuck of the electron beam welding machine, and evacuate to ≤5×10 - ³Pa; S202: Beam channel welding is carried out in the same furnace. The main welding fixture provides the preset axial force throughout the welding process to compensate for shrinkage in real time. S203: The reinforcing rib is positioned by spot welding on one side. The main welding fixture provides the preset axial force throughout the welding process, and the shrinkage is compensated in real time to obtain an ellipsoidal radio frequency superconducting cavity unit semi-finished product. Step S202 includes adjusting the welding current and beam diameter during the welding process, and performing multi-stage welding, including: S2021: Pre-sealing welding is performed using a voltage of 140KV~160KV, a current of 14.5mA~15.5mA, a welding rotation speed of 7mm / s~9mm / s, and a beam diameter of 3.8mm~4.5mm. S2022: Through welding is performed using a voltage of 140KV~160KV, a current of 18.5mA~19.5mA, a welding rotation speed of 7mm / s~9mm / s, and a beam diameter of 3.8mm~4.5mm. S2023: Modification welding is performed using a voltage of 140KV~160KV, a current of 15.8mA~16.5mA, a welding rotation speed of 7mm / s~9mm / s, and a beam diameter of 5.5mm~6.5mm.

2. The electron beam welding method for the intermediate dumbbell component of the ellipsoidal radio frequency superconducting cavity according to claim 1, characterized in that, The main welding fixture for the beam channel includes: a first handle, a first equatorial disk, an equatorial ring, and a first connecting rod; The first handle, the first equatorial disk, the equatorial ring, and the ellipsoidal radio frequency superconducting cavity unit are coaxially arranged. The area between the first equatorial disk and the equatorial ring is the fixed forming area of ​​the ellipsoidal radio frequency superconducting cavity unit. The first handle and the first equatorial disk are fixedly connected. The first equatorial disk and the equatorial ring are connected by a first connecting rod to press and fix the ellipsoidal radio frequency superconducting cavity unit between the first equatorial disk and the equatorial ring. The first equatorial disk is pressed and connected to the equatorial end of one half-unit in the ellipsoidal radio frequency superconducting cavity unit, and the equatorial ring is pressed and connected to the equatorial end of the other half-unit in the ellipsoidal radio frequency superconducting cavity unit. The beam channel ends of the two half-units are positioned and fixedly connected under the pressing action of the first connecting rod. The first connecting rod is connected to the first equatorial disk and / or equatorial ring at one end and is provided with a first elastic compensation structure. The first elastic compensation structure can provide a corrective force that is opposite to the deformation direction and positively correlated with the deformation amount when the beam channel ends of the two half-units are welded.

3. The electron beam welding method for the intermediate dumbbell component of the ellipsoidal radio frequency superconducting cavity according to claim 2, characterized in that, The first elastic compensation structure is a compression spring, the end of the first connecting rod is threaded, and the end of the first connecting rod passes through the compression spring and is fixed with a nut with matching pitch.

4. The electron beam welding method for the intermediate dumbbell component of the ellipsoidal radio frequency superconducting cavity according to any one of claims 2 or 3, characterized in that, The first connecting rod is provided in multiple parts, which are symmetrically arranged with respect to the axis center of the first equatorial disk and the equatorial ring.

5. The electron beam welding method for the intermediate dumbbell component of the ellipsoidal radio frequency superconducting cavity according to claim 1, characterized in that, The reinforcing rib welding and fixing fixture includes: a second handle, a second equatorial disk, a third equatorial disk, a central connecting rod, and a second elastic compensation structure; The second grip, the second equatorial disk, the third equatorial disk, and the ellipsoidal radio frequency superconducting cavity unit are coaxially arranged; the second grip and the second equatorial disk are fixedly connected. The second and third equatorial disks are disks with a central hole. The central connecting rod passes through the hollow area in the center of the first and third equatorial disks and can slide freely relative to the second and third equatorial disks. One end of the central connecting rod is fixedly connected to the second handle, and the second end is connected to the third equatorial disk through the second elastic compensation structure. The second elastic compensation structure is used to adjust the displacement of the second end of the central connecting rod relative to the third equatorial disk and to adjust the pressure applied by the second equatorial disk and the third equatorial disk to the ellipsoidal radio frequency superconducting cavity unit.

6. The electron beam welding method for the intermediate dumbbell component of the ellipsoidal radio frequency superconducting cavity according to claim 5, characterized in that, The second handle is provided with an internal threaded recess, and the end of the central connecting rod connected to the second handle is provided with an external thread that matches the pitch of the internal threaded recess.

7. The electron beam welding method for the intermediate dumbbell component of the ellipsoidal radio frequency superconducting cavity according to claim 5, characterized in that, The second elastic compensation structure is a spring. The central connecting rod is connected to the second elastic compensation structure at one end with an external thread and a matching nut. The central connecting rod passes through the second elastic compensation structure. One end of the second elastic compensation structure is connected to the nut, and the other end of the second elastic compensation structure is connected to the third equatorial disk, so that the displacement of the second elastic compensation structure is limited between the nut and the third equatorial disk.

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