Photocathode superconducting radio frequency electron gun

Abstract

The present invention relates to a photocathode superconducting radio frequency electron gun, comprising a quarter-wavelength resonant cavity, a first coaxial waveguide, and a second coaxial waveguide. The quarter-wavelength resonant cavity comprises cavity sidewalls, an anode portion, and a cathode portion. The anode portion is characterized in that: the anode portion comprises a cutoff waveguide arranged at the axis of the quarter-wavelength resonant cavity; the cutoff waveguide is connected to a bottom fillet of the anode surrounding it, and the bottom fillet of the anode is arched rearward; an anode top fillet is provided outside the bottom fillet of the anode, surrounding the cutoff waveguide and the bottom fillet, and arching forward; the top fillet of the anode and the bottom fillet are connected by a transition in the middle of the anode. The present invention provides a photocathode superconducting radio frequency cavity and a novel anode structure for a quarter-wavelength cavity, which generates a stronger electric field and a smaller magnetic field.

Description

Technical Field

[0001] The invention relates to a superconducting radio frequency cavity for a photocathode injector, belonging to the technical field of accelerators. Background Art

[0002] The photocathode superconducting radio frequency electron gun is primarily used to generate high-quality electron sources. It is internationally recognized as a device for generating high-quality electron sources in the future and is a candidate electron source for advanced light sources, free electron lasers, terahertz radiation, and systems based on high-quality electron beams. The photocathode superconducting radio frequency electron gun generates electrons by bombarding the photocathode with a laser, and then accelerates and extracts the electron beam under the action of a microwave field. The superconducting cavity structure used in high-frequency photocathode superconducting radio frequency electron guns is generally an elliptical cavity, while the superconducting cavity structure used in low-frequency photocathode superconducting radio frequency electron guns is generally a quarter-wave cavity. Due to the limitations of the anode structure optimization of the quarter-wave cavity, the field strength of the existing quarter-wave cavity is still relatively low, which is not conducive to improving the beam quality. Summary of the Invention

[0003] The technical problem to be solved by the present invention is that the field strength of the 1 / 4 wavelength cavity used in the existing photocathode superconducting radio frequency electron gun is still relatively low, which is not conducive to improving the beam quality.

[0004] In order to solve the above technical problems, the technical solution of the present invention is to provide a photocathode superconducting radio frequency electron gun, including a 1 / 4 wavelength resonant cavity, a first coaxial waveguide and a second coaxial waveguide. The second coaxial waveguide is coupled to the front of the 1 / 4 wavelength resonant cavity, and the first coaxial waveguide and the second coaxial waveguide are coupled to each other via a tube-tube coupling unit. The 1 / 4 wavelength resonant cavity includes a cavity sidewall, an anode portion provided on the front of the cavity sidewall, and a cathode portion provided on the back of the cavity sidewall. The invention is characterized in that: the anode portion includes a cutoff waveguide arranged at the axis of the 1 / 4 wavelength resonant cavity, and the second coaxial waveguide is coupled to the cutoff waveguide via the cavity-tube coupling unit; the cutoff waveguide is connected to the anode bottom fillet surrounding it, and the anode bottom fillet is arched backward; an anode top fillet surrounding the cutoff waveguide and the anode bottom fillet is provided outside the anode bottom fillet, and the anode top fillet is arched forward; the anode top fillet and the bottom fillet are connected by an anode middle transition portion, and the anode middle portion is inclined from the outside to the inside from the position of the anode top fillet to the position of the bottom fillet; and the anode top fillet is connected to the cavity sidewall.

[0005] The longitudinal cross-sectional profiles of the top and bottom rounded corners of the anode are top arcs and bottom arcs that are symmetrical about the axis of the 1 / 4 wavelength resonant cavity, and the longitudinal cross-sectional profile of the middle part of the anode is two tangent lines that are symmetrical about the axis of the 1 / 4 wavelength resonant cavity 1; each tangent line is tangent to the top arc and bottom arc at the same position.

[0006] Preferably, the tangent line is a straight line or an arc.

[0007] Preferably, the curvature radius of the top arc is R at , the curvature radius of the bottom arc is R ab , then R at With R ab The relationship is: R at >R ab .

[0008] Preferably, the angle between the tangent line and the arc at the bottom of the anode is θ a , angle θ a The value is less than 90 degrees.

[0009] Preferably, the cathode part adopts a nose cone structure that arches forward, including a cathode fillet and a cathode nose cone tail connected to the side wall of the cavity; a cathode is provided at the axial center position of the front end surface of the cathode fillet; the cathode fillet and the cathode nose cone tail are connected by a cathode nose cone inclined surface transition.

[0010] This invention provides a photocathode superconducting radio frequency electron gun that solves the problem of optimizing the anode structure for a quarter-wavelength cavity. Unlike existing quarter-wavelength resonant cavities, the angle between the middle of the anode and the fillet at the bottom of the anode is less than 90 degrees. This causes the anode to protrude outward, forming a nose cone. This increases the magnetic flux across the cross section, generating a stronger electric field along the axis. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a structural schematic diagram of the present invention;

[0012] Figure 2 It is a cross-sectional schematic diagram of the present invention;

[0013] Figure 3 is a longitudinal sectional front view of an embodiment according to the present invention;

[0014] Figure 4 for Figure 3 Anode profile in the middle cavity. DETAILED DESCRIPTION

[0015] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0016] like Figure 1 As shown, the photocathode superconducting radio frequency electron gun provided by the present invention includes a 1 / 4 wavelength resonant cavity 1, a first coaxial waveguide 2 and a second coaxial waveguide 3. The second coaxial waveguide 3 is coupled to the front of the 1 / 4 wavelength resonant cavity 1. Figure 3 The first coaxial waveguide tube 2 and the second coaxial waveguide tube 3 are coupled and connected via a tube-tube coupling unit 14 .

[0017] Combine Figure 2 In this embodiment, the 1 / 4 wavelength resonant cavity 1 is composed of multiple parts, including a cavity side wall 12, and the front side of the cavity side wall 12 is provided with an anode part and the back side is provided with a cathode part.

[0018] The anode part includes a cutoff waveguide 7 arranged at the axis of the 1 / 4 wavelength resonant cavity 1, combined with Figure 3 , the second coaxial waveguide tube 3 is coupled to the cutoff waveguide 7 through the cavity-tube coupling unit 13. The cutoff waveguide 7 is connected to the anode bottom fillet 6 that surrounds it, and the anode bottom fillet 6 is arched backward. The outside of the anode bottom fillet 6 is provided with an anode top fillet 4 that surrounds the cutoff waveguide 7 and the anode bottom fillet 6, and the anode top fillet 4 is arched forward. The anode top fillet 4 and the bottom fillet 6 are transitionally connected by the anode middle part 5. From the position of the anode top fillet 4 to the position of the bottom fillet 6, the anode middle part 5 is inclined from the outside to the inside. The anode top fillet 4 is connected to the cavity side wall 12.

[0019] Combine Figure 3 as well as Figure 4 The longitudinal cross-sectional profiles of the top fillet 4 and the bottom fillet 6 of the anode are a top arc 16 and a bottom arc 18 that are symmetrical about the axis of the 1 / 4 wavelength resonant cavity 1. The longitudinal cross-sectional profile of the middle portion 5 of the anode is two tangent lines 17 that are symmetrical about the axis of the 1 / 4 wavelength resonant cavity 1. The tangent lines 17 are tangent to the top arc 16 and the bottom arc 18 at the same position. The tangent lines 17 can be straight lines or arcs. In this embodiment, the tangent lines 17 are straight lines. The curvature radius of the top arc 16 is R at , the curvature radius of the bottom arc 18 is R ab , then R at With R ab The relationship is: R at >R abThe angle between the tangent line 17 and the arc 18 at the bottom of the anode is θ a , angle θ a The value is less than 90 degrees.

[0020] The cathode portion adopts a forward-arching nose cone structure, including a cathode fillet 9 and a cathode nose cone tail 11 connected to the cavity sidewall 12. A cathode 8 is provided at the axial center of the front end of the cathode fillet 9. The cathode fillet 9 and the cathode nose cone tail 11 are transitionally connected by a cathode nose cone bevel 10.

Claims

1. A photocathode superconducting radio frequency electron gun, comprising a quarter-wavelength resonant cavity, a first coaxial waveguide, and a second coaxial waveguide, wherein the second coaxial waveguide is coupled to the front face of the quarter-wavelength resonant cavity, and the first coaxial waveguide and the second coaxial waveguide are coupled to each other via a tube-tube coupling unit, wherein: The 1 / 4 wavelength resonant cavity comprises a cavity side wall, an anode portion arranged on the front side wall of the cavity, and a cathode portion arranged on the back side wall of the cavity, and is characterized in that: the anode portion comprises a cutoff waveguide arranged at the axis of the 1 / 4 wavelength resonant cavity, and a second coaxial waveguide tube is coupled to the cutoff waveguide via a cavity-tube coupling unit; the cutoff waveguide is connected to the bottom fillet of the anode surrounding it, and the bottom fillet of the anode is arched backward; an anode top fillet surrounding the cutoff waveguide and the bottom fillet of the anode is provided on the outside of the bottom fillet of the anode, and the top fillet of the anode is arched forward; the top fillet of the anode and the bottom fillet are connected by a transition between the middle part of the anode, and the middle part of the anode is inclined from the outside to the inside from the position of the top fillet of the anode to the position of the bottom fillet; the top fillet of the anode is connected to the cavity side wall; The longitudinal cross-sectional profiles of the top and bottom rounded corners of the anode are top arcs and bottom arcs that are symmetrical up and down with the axis of the 1 / 4 wavelength resonant cavity as the axis, and the longitudinal cross-sectional profile of the middle part of the anode are two tangent lines that are symmetrical up and down with the axis of the 1 / 4 wavelength resonant cavity as the axis; each tangent line is tangent to the top arc and bottom arc at the same position.

2. A photocathode superconducting radio frequency electron gun according to claim 1, characterized in that: The tangent line is a straight line or an arc.

3. The photocathode superconducting radio frequency electron gun according to claim 1, characterized in that: The curvature radius of the top arc is R at , the curvature radius of the bottom arc is R ab , then R at With R ab The relationship is: R at >R ab .

4. The photocathode superconducting radio frequency electron gun according to claim 1, characterized in that: The angle between the tangent line and the arc at the bottom of the anode is θ a , angle θ a The value is less than 90 degrees.

5. The photocathode superconducting radio frequency electron gun according to claim 1, characterized in that: The cathode part adopts a nose cone structure that arches forward, including a cathode fillet and a cathode nose cone tail connected to the side wall of the cavity; a cathode is provided at the axial center position of the front end surface of the cathode fillet; the cathode fillet and the cathode nose cone tail are connected by a cathode nose cone inclined surface transition.

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