Auxiliary measurement tool and measurement method for overall cavity size and form and location tolerance of radio frequency superconducting cavity

Abstract

The invention discloses an auxiliary measurement tool and method for the whole cavity size and form and location tolerance of a radio frequency superconducting cavity, and the method comprises the following steps: S1, assembling an auxiliary measurement tool, and assembling a dumbbell on the auxiliary measurement tool for measurement; s2, measuring the size and form and location tolerance of the dumbbell; s3, assembling an auxiliary measurement tool, and assembling the whole radio frequency superconducting cavity on the auxiliary measurement tool for measurement; and S4, measuring the size and form and location tolerance of the whole radio frequency superconducting cavity. By manufacturing a special tool and designing a measurement scheme, the problems of one-time fixation of the dumbbell and simultaneous measurement of the upper and lower half bowls are solved, the upper and lower equatorial planes can be measured at the same time, and the dumbbell height is accurately evaluated. If the three-coordinate measuring platform is large enough, multiple sets of measuring tools can be manufactured, multiple dumbbells can be measured at a time, the problem of batch measurement is solved, the machining quality of the dumbbell and the whole cavity can be controlled, and the measuring efficiency is at least improved by 50%.

Description

Technical Field

[0001] The present invention relates to the technical field of radio frequency superconducting cavities, and particularly to an auxiliary measuring tool and a measuring method for the overall cavity size and geometric tolerance of a radio frequency superconducting cavity. Background Art

[0002] The 3.9GHz - 9cell radio frequency superconducting cavity is mainly applied to the accelerator of the Shanghai Free Electron Laser Hard X-ray Facility (SHINE), used to accelerate electrons and compensate for the long bunch non-linear longitudinal distortion caused by the acceleration field of the 1.3GHz - 9cell cavity, and improve the peak bunch current intensity. This cavity is mainly composed of 9 dumbbells and two end cavity components on the left and right welded together. The dumbbells account for one-third of the entire cavity component, and the manufacturing precision and efficiency of the dumbbells directly affect the manufacturing level and progress of the overall cavity. In the prior art, the measurement of the dumbbells is mainly to place one equatorial plane of the dumbbell on the measurement platform and measure data such as the diameter, roundness, and surface profile of the upper half bowl. Then turn it over and place the upper equatorial plane on the measurement platform to measure data such as the diameter, roundness, and surface profile of the lower half bowl. In this measurement method, there is always one equatorial plane in contact with the measurement platform during the measurement process, and the two equatorial planes cannot be measured simultaneously, so the height of the dumbbell cannot be accurately measured; moreover, after measuring one half bowl, the workpiece needs to be turned over and fixed again, resulting in low measurement efficiency, a longer manufacturing cycle for the overall cavity, and a reduction in manufacturing efficiency. Summary of the Invention

[0003] In order to solve the technical problems existing in the above technologies, in view of this, it is necessary to provide an auxiliary measuring tool for the overall cavity size and geometric tolerance of a radio frequency superconducting cavity.

[0004] An auxiliary measuring tool for the overall cavity size and geometric tolerance of a radio frequency superconducting cavity includes a standard flat plate and a positioning component installed on the standard flat plate for fixing the dumbbell; the positioning component includes an upper positioning plate and a lower positioning plate; the lower positioning plate is installed on the standard flat plate, and the upper end of the lower positioning plate has a first curved surface adapted to the external contour of the overall radio frequency superconducting cavity. The upper positioning plate is installed directly above the lower positioning plate, and the lower end of the upper positioning plate has a second curved surface adapted to the external contour of the overall radio frequency superconducting cavity. After the upper positioning plate and the positioning plate are assembled and aligned, the first curved surface and the second curved surface are in contact with the outer surface of the dumbbell.

[0005] Preferably, lower through holes are symmetrically opened on both sides of the upper end of the lower positioning plate at the first curved surface, upper through holes penetrating the upper positioning plate are symmetrically opened on both sides of the upper end of the upper positioning plate at the second curved surface, and the upper through holes and the lower through holes are fixed by screws.

[0006] Preferably, connection holes are opened on both sides of the lower end of the lower positioning plate, positioning holes adapted to the connection holes are opened on the standard flat plate, and the connection holes and the positioning holes are fixed by screws.

[0007] Preferably, a measurement platform for placing the standard flat plate is further provided below the standard flat plate.

[0008] Preferably, the first curved surface and the second curved surface have the same structure. The first curved surface includes an arc-shaped groove formed at the middle position of the upper end of the lower positioning plate, and arc-shaped inclined surfaces symmetrically formed on both sides of the arc-shaped groove and adapted to the outer contour of the dumbbell. The arc-shaped inclined surfaces extend downward along the two side edges of the arc-shaped groove, and the surface of the arc-shaped inclined surface is spherical.

[0009] It is also necessary to provide a method for measuring the overall cavity size and form and position tolerances of a radio frequency superconducting cavity.

[0010] A method for measuring the overall cavity size and form and position tolerances of a radio frequency superconducting cavity, which uses the above-mentioned radio frequency superconducting cavity overall cavity size and form and position tolerance auxiliary measurement tooling for measurement, includes the following steps. Step S1: Assemble the auxiliary measurement tooling, and assemble the dumbbell on the auxiliary measurement tooling for measurement. Step S2: Measure the size and form and position tolerances of the dumbbell. Step S3: Assemble the auxiliary measurement tooling, and assemble the radio frequency superconducting cavity overall cavity on the auxiliary measurement tooling for measurement. Step S4: Measure the size and form and position tolerances of the radio frequency superconducting cavity overall cavity.

[0011] Preferably, in step S1, the dumbbell is assembled on the auxiliary measurement tooling in the following manner. S11: Place the standard flat plate on the measurement platform, align the threaded holes on the measurement platform with the positioning holes on the standard flat plate, use bolts to fix the standard flat plate on the measurement platform, and ensure that the length and width of the standard flat plate are less than the stroke of the coordinate measuring machine. S12: Place the lower positioning plate on the standard flat plate, align the connection holes on the lower positioning plate with the positioning holes on the standard flat plate, use screws to fix the lower positioning plate and the standard flat plate, and ensure firm installation. S13: Place the dumbbell in the first curved surface at the upper end of the lower positioning plate, and make the first curved surface fit the outer surface of the dumbbell. S14: Place the upper positioning plate on the dumbbell, make the second curved surface at the lower end of the upper positioning plate fit the outer surface of the dumbbell, and ensure that the upper through hole and the lower through hole are aligned. Insert two screws into the upper through hole and the lower through hole respectively, and tighten them by hand to confirm that the dumbbell does not move. Preferably, in step S2, the size and form and position tolerances of the dumbbell are measured in the following manner. S21: Insert the 3D model, adjust the origin position and axis direction of the 3D model to be exactly the same as the origin and axis direction established by the half-bowl plan. S22: Manually establish a coordinate system using the left semi-bowl equatorial plane and the outer circle of the left semi-bowl equator to establish the coordinate system; S23: Automatically establish a coordinate system using the left semi-bowl equatorial plane and the outer circle of the left semi-bowl equator to establish the coordinate system, and coincide the coordinate system with the 3D model coordinate system; S24: After the coordinate system is established, measure the parameters to be evaluated on the left semi-bowl; S25: Use the automatic measuring point function of the coordinate measuring machine to collect points on the inner contour surface of the left semi-bowl 3D model. After the point collection is completed, fit all the points into a feature group and evaluate the surface profile of the fitted feature group, that is, complete the evaluation of the inner surface profile of the left semi-bowl; S26: Repeat steps S22 to S26 to complete the evaluation of the basic dimensions and inner surface profile of the right semi-bowl, and then select the equatorial planes of the left and right semi-bowls and use the 3D shortest distance to evaluate the dumbbell height.

[0012] Preferably, in step S3, the whole radio frequency superconducting cavity is assembled on the auxiliary measuring fixture in the following manner. S31: Place the standard flat plate on the measuring platform, align the threaded holes on the measuring platform with the positioning holes on the standard flat plate, and use bolts to fix the standard flat plate on the measuring platform, and ensure that the length and width of the standard flat plate should be less than the travel of the coordinate measuring machine; S32: Place the two lower positioning plates on the standard flat plate at equal intervals facing each other, make the first curved surfaces on the two lower positioning plates coaxial, ensure that the connecting holes on the lower positioning plates are facing the positioning holes on the standard flat plate, and use screws to fix the lower positioning plates to the standard flat plate to ensure firm installation; S33: Place the whole radio frequency superconducting cavity on the first curved surfaces at the upper ends of the two lower positioning plates, make the first curved surface fit with the outer surface of the whole radio frequency superconducting cavity, and use a glue stick to fix the whole radio frequency superconducting cavity to the lower positioning plate.

[0013] Preferably, in step S4, measure the dimensions and geometric tolerances of the whole radio frequency superconducting cavity in the following manner. S41: Insert the 3D model, adjust the origin position and axis direction of the 3D model coordinate axis to make the origin and axis direction of the whole cavity plan exactly the same; S42: Manually establish a coordinate system using the center connection line of the left and right reference ring circles as the Y-axis, project the center point of the coupling flange outer cylinder onto the Y-axis as the origin O, and use the connection line between the center of the coupling flange outer cylinder and the origin O as the X-axis; S43: Automatic coordinate system, use the center connection line of the left and right reference ring circles as the Y-axis, project the center point of the coupling flange outer cylinder onto the Y-axis as the origin O, and use the connection line between the center of the coupling flange outer cylinder and the origin O as the X-axis, and coincide the coordinate system with the 3D model coordinate system; S44: After the coordinate system is established, measure the outer circle or outer cylinder of the equator and the flange plane of each cell in the middle, and complete the concentricity evaluation of each cell in the whole cavity with the Y-axis reference and the evaluation of the length of the whole cavity.

[0014] Compared with the prior art, an auxiliary measurement tooling and measurement method for the overall dimensions and geometric tolerances of a radio frequency superconducting cavity provided by the present invention solve the problem of simultaneously measuring the upper and lower half bowls with a single fixation of the dumbbell by making special tooling and designing a measurement scheme, and can simultaneously measure the upper and lower equatorial planes to accurately evaluate the height of the dumbbell. If the coordinate measuring platform is large enough, multiple sets of this measurement tooling can be manufactured to achieve the measurement of multiple dumbbells at one time, which not only solves the problem of batch measurement, but also can control the processing quality of the dumbbell and the overall cavity, and the measurement efficiency is increased by at least 50%. At the same time, it can solve the problems of lack of tooling fixation for overall cavity measurement and difficulty in batch measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0016] Figure 1 It is a schematic structural diagram of the auxiliary measurement tooling of the present invention.

[0017] Figure 2 For the present invention Figure 1 is a schematic side view structure diagram.

[0018] Figure 3 It is a schematic structural diagram of the lower positioning plate of the present invention.

[0019] Figure 4 For the present invention Figure 3 is a schematic structural diagram from another angle.

[0020] Figure 5 It is a schematic structural diagram of the upper positioning plate of the present invention.

[0021] Figure 6 It is a schematic diagram of the present invention using the equatorial plane and the outer circle of the equator to establish a coordinate system.

[0022] Figure 7 It is a schematic diagram of the present invention using the equatorial plane and the outer circle of the equator to establish a coordinate system.

[0023] Figure 8 It is a schematic structural diagram of the auxiliary measurement tooling of the present invention after being assembled with the overall cavity.

[0024] Figure 9Schematic diagram for establishing a coordinate system during the integral cavity measurement of the present invention.

[0025] In the figure: standard flat plate 01, upper positioning plate 02, lower positioning plate 03, first curved surface 04, arc-shaped groove 41, arc-shaped inclined surface 42, second curved surface 05, lower through-hole 06, upper through-hole 07, connection hole 08, positioning hole 09, measurement platform 10, integral cavity 20, positioning assembly 30, dumbbell 40. Specific embodiments

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0027] In the description of the present invention, it should be understood that the terms "upper", "middle", "outer", "inner", "lower", etc. indicating the orientation or position relationship are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the components or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0028] Please refer to Figures 1 to 5 , in one embodiment, the present invention provides an auxiliary measurement tool for the integral cavity size and form and position tolerances of a radio frequency superconducting cavity, including a standard flat plate 01 and a positioning assembly 30 installed on the standard flat plate 01 for fixing the dumbbell; wherein, the positioning assembly 30 includes an upper positioning plate 02 and a lower positioning plate 03; the lower positioning plate 03 is installed on the standard flat plate 01, and the upper end of the lower positioning plate 03 has a first curved surface 04 adapted to the external contour of the integral cavity of the radio frequency superconducting cavity, the upper positioning plate 02 is installed directly above the lower positioning plate 03, and the lower end of the upper positioning plate 02 has a second curved surface 05 adapted to the external contour of the integral cavity of the radio frequency superconducting cavity. After the upper positioning plate 02 and the positioning plate are assembled and aligned, the first curved surface 04 and the second curved surface 05 are in contact with the outer surface of the dumbbell.

[0029] Among them, lower through-holes 06 are symmetrically opened on both sides of the upper end of the lower positioning plate 03 at the first curved surface 04, upper through-holes 07 penetrating through the upper positioning plate 02 are symmetrically opened on both sides of the upper end of the upper positioning plate 02 at the second curved surface 05, and the upper through-holes 07 and the lower through-holes 06 are fixed by a penetrating screw rod. Of course, the lower through-holes 06 can also be threaded holes, while the upper through-holes 07 are non-threaded holes. The screw rod is inserted into the upper through-holes 07 and then screwed into the lower through-holes 06 to achieve fixation.

[0030] Among them, connection holes 08 are provided on both sides at the lower end of the lower positioning plate 03, and positioning holes 09 adapted to the connection holes 08 are provided on the standard flat plate 01. The connection holes 08 and the positioning holes 09 are fixed by screws.

[0031] Among them, a measuring platform 10 for placing the standard flat plate 01 is further provided below the standard flat plate 01; and the measuring platform 10 is a coordinate measuring platform.

[0032] Among them, the structures of the first curved surface 04 and the second curved surface 05 are the same. The first curved surface 04 includes an arc-shaped groove 41 formed at the middle position of the upper end of the lower positioning plate 03, and arc-shaped inclined surfaces 42 symmetrically formed on both sides of the arc-shaped groove 41 and adapted to the outer contour of the dumbbell. The arc-shaped inclined surfaces 42 extend downward along the two side edges of the arc-shaped groove 41, and the surface of the arc-shaped inclined surface 42 is spherical, so as to be adapted to the outer contour of the dumbbell. When the lower positioning plate 03 and the upper positioning plate 02 are assembled and aligned, it can be ensured that the first curved surface 04 and the second curved surface 05 are completely attached to the outer contour of the dumbbell.

[0033] In one embodiment, taking a 3.9GHz - 9cell radio frequency superconducting cavity as an example, the present invention provides a method for measuring the overall cavity size and form and position tolerances of a radio frequency superconducting cavity, including the following steps. Step S1: Assemble the auxiliary measuring tooling, and assemble the dumbbell on the auxiliary measuring tooling for measurement. Step S2: Measure the size and form and position tolerances of the dumbbell. Step S3: Assemble the auxiliary measuring tooling, and assemble the overall radio frequency superconducting cavity on the auxiliary measuring tooling for measurement. Step S4: Measure the size and form and position tolerances of the overall radio frequency superconducting cavity.

[0034] Specifically, in step S1, the dumbbell is assembled on the auxiliary measuring tooling in the following manner. S11: Place the standard flat plate 01 on the measuring platform 10, align the threaded holes on the measuring platform 10 with the positioning holes 09 on the standard flat plate 01, use bolts to fix the standard flat plate 01 on the measuring platform 10, and ensure that the length and width of the standard flat plate 01 are less than the stroke of the coordinate measuring machine. S12: Place the lower positioning plate 03 on the standard flat plate 01, align the connection holes 08 on the lower positioning plate 03 with the positioning holes 09 on the standard flat plate 01, and use screws to fix the lower positioning plate 03 and the standard flat plate 01 to ensure firm installation. S13: Place the dumbbell in the first curved surface 04 at the upper end of the lower positioning plate 03, so that the first curved surface 04 is in contact with the outer surface of the dumbbell. S14: Place the upper positioning plate 02 on top of the dumbbell, such that the second curved surface 05 at the lower end of the upper positioning plate 02 fits snugly against the outer surface of the dumbbell, and ensure that the upper through-hole 07 is aligned directly with the lower through-hole 06. Insert the two screws into the upper through-hole 07 and the lower through-hole 06 respectively, and tighten them by hand to confirm that the dumbbell is fixed in place; Please refer to Figure 6 , Figure 7 , and specifically elaborate as follows. In step S2, the dimensions and geometric tolerances of the dumbbell are measured through the following methods, S21: Insert the 3D model, and adjust the origin position and axis directions of the 3D model to be exactly the same as those of the coordinate system established in the half-bowl plan; S22: Manually establish a coordinate system using the left half-bowl equatorial plane and the outer circle of the left half-bowl equator; S23: Automatically establish a coordinate system using the left half-bowl equatorial plane and the outer circle of the left half-bowl equator, and align the coordinate system with the 3D model coordinate system; S24: After the coordinate system is established, measure the parameters to be evaluated for the left half-bowl, such as the evaluation of the half-bowl diameter, roundness, and flatness; S25: Use the three-coordinate automatic point measurement function to collect points on the inner contour surface of the left half-bowl 3D model. The positions of the collected points should cover all the inner contour surfaces as much as possible. The greater the point density, the closer the fitted inner contour surface is to the true contour. After the point collection is completed, fit all the points into a feature group and evaluate the surface profile of the fitted feature group, thus completing the evaluation of the inner surface profile of the left half-bowl; S26: Repeat steps S22 to S26 to complete the evaluation of the basic dimensions and inner surface profile of the right half-bowl, and then select the equatorial planes of the left and right half-bowls and use the three-dimensional shortest distance to evaluate the height of the dumbbell.

[0035] Please refer to Figure 8 , and specifically elaborate as follows. In step S3, the entire radio frequency superconducting cavity is assembled on the auxiliary measurement fixture through the following methods, S31: Place the standard flat plate 01 on the measurement platform 10, align the threaded holes on the measurement platform 10 with the positioning holes 09 on the standard flat plate 01, and use bolts to fix the standard flat plate 01 on the measurement platform 10, ensuring that the length and width of the standard flat plate 01 are less than the travel of the coordinate measuring machine; S32: Place the two lower positioning plates 03 opposite each other and equidistantly on the standard flat plate 01, such that the first curved surfaces 04 on the two lower positioning plates 03 are coaxial, ensure that the connection holes 08 on the lower positioning plates 03 are aligned directly with the positioning holes 09 on the standard flat plate 01, and use screws to fix the lower positioning plates 03 to the standard flat plate 01 to ensure a firm installation; S33: Place the entire radio frequency superconducting cavity within the first curved surface 04 at the upper ends of the two lower positioning plates 03, such that the first curved surface 04 conforms to the outer surface curve of the entire radio frequency superconducting cavity, and use a glue stick to fix the entire radio frequency superconducting cavity to the lower positioning plates 03.

[0036] Please refer to Figure 9 , and specifically elaborate that in step S4, the dimensions and geometric tolerances of the entire radio frequency superconducting cavity are measured in the following manner S41: Insert the 3D model, and adjust the origin position and axis directions of the 3D model coordinate axes to make them exactly the same as those of the entire cavity plan. S42: Manually establish a coordinate system. Use the center connection line of the left and right reference ring circles as the Y-axis, project the center point of the outer cylinder of the coupling flange onto the Y-axis as the origin O, and use the connection line between the center of the outer cylinder of the coupling flange and the origin O as the X-axis. S43: For the automatic coordinate system, use the center connection line of the left and right reference ring circles as the Y-axis, project the center point of the outer cylinder of the coupling flange onto the Y-axis as the origin O, and use the connection line between the center of the outer cylinder of the coupling flange and the origin O as the X-axis, and make the coordinate system coincide with the 3D model coordinate system. S44: After the coordinate system is established, measure the outer equatorial circle or outer cylinder and the flange plane of the middle 9 cells to complete the concentricity evaluation of the 9 cells of the entire cavity with respect to the Y-axis reference and the evaluation of the entire cavity length.

[0037] The above-disclosed are only the preferred embodiments of the present invention. Of course, the scope of the rights of the present invention cannot be limited thereby. Those of ordinary skill in the art can understand the implementation of all or part of the above processes, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. An auxiliary measuring tool for the overall cavity size and geometric tolerance of a radio frequency superconducting cavity, characterized in that: It includes a standard flat plate and a positioning component installed on the standard flat plate for fixing dumbbells; the positioning component includes an upper positioning plate and a lower positioning plate; the lower positioning plate is installed on the standard flat plate, and the upper end of the lower positioning plate has a first curved surface adapted to the outer contour of the dumbbell. The upper positioning plate is installed directly above the lower positioning plate, and the lower end of the upper positioning plate has a second curved surface adapted to the outer contour of the dumbbell. After the upper positioning plate and the positioning plate are assembled and aligned, the first curved surface and the second curved surface are in contact with the outer surface of the dumbbell.

2. The radio frequency superconducting cavity overall cavity size and geometric tolerance auxiliary measurement tooling according to claim 1, wherein: On both sides of the upper end of the lower positioning plate, lower through holes are symmetrically opened on both sides of the first curved surface. On both sides of the upper end of the upper positioning plate, upper through holes penetrating the upper positioning plate are symmetrically opened. The upper through holes and the lower through holes are fixed by screws.

3. The radio frequency superconducting cavity integral cavity size and geometric tolerance auxiliary measurement tooling according to claim 2, characterized in that: On both sides of the lower end of the lower positioning plate, connection holes are opened. On the standard flat plate, positioning holes adapted to the connection holes are opened. The connection holes and the positioning holes are fixed by screws.

4. The radio frequency superconducting cavity integral cavity size and geometric tolerance auxiliary measurement tooling according to claim 1, characterized in that: Below the standard flat plate, a measuring platform for placing the standard flat plate is also provided.

5. The radio frequency superconducting cavity integral cavity size and geometric tolerance auxiliary measurement tooling according to claim 1, characterized in that: The structures of the first curved surface and the second curved surface are the same. The first curved surface includes an arc-shaped groove formed at the middle position of the upper end of the lower positioning plate, and arc-shaped inclined surfaces symmetrically formed on both sides of the arc-shaped groove and adapted to the outer contour of the dumbbell. The arc-shaped inclined surfaces extend downward along the two side edges of the arc-shaped groove, and the surface of the arc-shaped inclined surface is spherical.

6. A method for measuring the overall cavity size and geometric tolerance of a radio frequency superconducting cavity, which uses the auxiliary measuring tooling for the overall cavity size and geometric tolerance of the radio frequency superconducting cavity described in any one of claims 1-5 for measurement, and is characterized in that: It includes the following steps Step S1: Assemble the auxiliary measuring tooling and assemble the dumbbell on the auxiliary measuring tooling for measurement; Step S2: Measure the dimensions and geometric tolerances of the dumbbell; Step S3: Assemble the auxiliary measuring tooling and assemble the entire radio frequency superconducting cavity on the auxiliary measuring tooling for measurement; Step S4: Measure the dimensions and geometric tolerances of the entire radio frequency superconducting cavity.

7. The method for measuring the overall cavity size and geometric tolerance of a radio frequency superconducting cavity according to claim 6, wherein: In step S1, the dumbbell is assembled on the auxiliary measuring tooling in the following way S11: Place the standard flat plate on the measuring platform, align the threaded holes on the measuring platform with the positioning holes on the standard flat plate, and use bolts to fix the standard flat plate on the measuring platform, and ensure that the length and width of the standard flat plate are less than the stroke of the coordinate measuring machine; S12: Place the lower positioning plate on the standard flat plate, align the connection holes on the lower positioning plate with the positioning holes on the standard flat plate, and use screws to fix the lower positioning plate and the standard flat plate to ensure firm installation; S13: Place the dumbbell in the first curved surface at the upper end of the lower positioning plate, so that the first curved surface is in contact with the curved surface of the outer surface of the dumbbell; S14: Place the upper positioning plate on the dumbbell, so that the second curved surface at the lower end of the upper positioning plate is in contact with the curved surface of the outer surface of the dumbbell, and ensure that the upper through holes and the lower through holes are aligned. Insert two screws into the upper through holes and the lower through holes respectively, and tighten them by hand to confirm that the dumbbell does not move.

8. The method for measuring the overall dimensions and geometric tolerances of a radio frequency superconducting cavity according to claim 7, wherein: In step S2, the dimensions and geometric tolerances of the dumbbell are measured in the following way S21: Insert the 3D model, adjust the origin position and axis direction of the 3D model coordinate axis to be exactly the same as the origin and axis direction established by the half-bowl plan; S22: Manually establish a coordinate system, and use the left half-bowl equatorial plane and the left half-bowl equatorial outer circle to establish a coordinate system; S23: Automatically establish a coordinate system. Use the left semi-bowl equatorial plane and the outer circle of the left semi-bowl equator to establish the coordinate system, and make the established coordinate system coincide with the three-dimensional model coordinate system; S24: After the coordinate system is established, measure the parameters to be evaluated for the left semi-bowl; S25: Use the three-coordinate automatic point measurement function to collect points on the inner contour surface of the left semi-bowl three-dimensional model. After the point collection is completed, fit all the points into a feature group and evaluate the surface profile of the fitted feature group, thus completing the evaluation of the inner surface profile of the left semi-bowl; S26: Repeat steps S22 to S26 to complete the evaluation of the basic dimensions and inner surface profile of the right semi-bowl. Then select the equatorial planes of the left and right semi-bowls and use the three-dimensional shortest distance to evaluate the dumbbell height.

9. The method for measuring the overall cavity size and geometric tolerance of a radio frequency superconducting cavity according to claim 8, wherein: In step S3, the whole radio frequency superconducting cavity is assembled on the auxiliary measurement tooling in the following way. S31: Place the standard flat plate on the measurement platform, align the threaded holes on the measurement platform with the positioning holes on the standard flat plate, and use bolts to fix the standard flat plate on the measurement platform, ensuring that the length and width of the standard flat plate are less than the travel of the coordinate measuring machine; S32: Place the two lower positioning plates on the standard flat plate in opposite directions at equal intervals, making the first curved surfaces on the two lower positioning plates coaxial, ensuring that the connection holes on the lower positioning plates are directly opposite the positioning holes on the standard flat plate, and use screws to fix the lower positioning plates to the standard flat plate to ensure firm installation; S33: Place the whole radio frequency superconducting cavity within the first curved surfaces at the upper ends of the two lower positioning plates, making the first curved surfaces fit with the outer surface of the whole radio frequency superconducting cavity, and use a glue stick to fix the whole radio frequency superconducting cavity to the lower positioning plates.

10. The method for measuring the overall dimensions and geometric tolerances of a radio frequency superconducting cavity according to claim 9, characterized in that: In step S4, measure the dimensions and form and position tolerances of the whole radio frequency superconducting cavity in the following way. S41: Insert the three-dimensional model, adjust the origin position and axis direction of the three-dimensional model coordinate axis to make the origin and axis direction of the whole cavity plan exactly the same; S42: Manually establish a coordinate system. Use the center connection line of the left and right reference ring circles as the Y-axis, project the center point of the coupling flange outer cylinder onto the Y-axis as the origin O, and use the connection line between the center of the coupling flange outer cylinder and the origin O as the X-axis; S43: Automatically establish a coordinate system. Use the center connection line of the left and right reference ring circles as the Y-axis, project the center point of the coupling flange outer cylinder onto the Y-axis as the origin O, and use the connection line between the center of the coupling flange outer cylinder and the origin O as the X-axis, and make the established coordinate system coincide with the three-dimensional model coordinate system; S44: After the coordinate system is established, measure the outer circle or outer cylinder of the equator and the flange plane of each cell in the middle to complete the concentricity evaluation of each cell of the whole cavity with respect to the Y-axis reference and the evaluation of the whole cavity length.

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