CN220065615U

CN220065615U - Cathode laser back heating mechanism and long-service-life electron gun and X-ray source with same

Info

Publication number: CN220065615U
Application number: CN202321647846.5U
Authority: CN
Inventors: 彭宇飞; 龙继东; 李建北; 赵伟; 张邦建; 李燕; 陶小魁; 彭攀; 陈弹蛋
Original assignee: Changzhou Huashu Technology Co ltd
Current assignee: Changzhou Huashu Technology Co ltd
Priority date: 2023-06-27
Filing date: 2023-06-27
Publication date: 2023-11-21
Anticipated expiration: 2033-06-27

Abstract

The utility model discloses a cathode laser back heating mechanism and an electron gun and an X-ray source with the same and long service life. The cathode laser back heating mechanism comprises an emitter, a cathode structural member, a window and a laser, wherein the emitter, the cathode structural member and the window jointly form a cavity, the cavity is provided with an exhaust hole, the laser is used for generating laser, a shielding cover is arranged on the cathode structural member, the emitter, the cathode structural member and the shielding cover jointly form an inner cavity, the inner cavity is of a closed cavity structure, only a laser through hole is formed in the shielding cover, and the laser penetrates through the window and enters the inner cavity through the laser through hole. The utility model reduces the evaporation of cathode substances from the evaporation path of pollutants by arranging the small-hole through-focusing-pollution storage structure, and further reduces the evaporation of the cathode substances from the source by arranging the high-temperature pollution barrier structure at the cathode interface, thereby solving the problems of insulation breakdown and optical system pollution caused by cathode evaporation.

Description

Cathode laser back heating mechanism and long-service-life electron gun and X-ray source with same

Technical Field

The utility model belongs to the technical field of laser back heating electron guns, and particularly relates to a cathode laser back heating mechanism, a long-service-life electron gun with the cathode laser back heating mechanism and an X-ray source.

Background

The main stream heat emission electron gun generally adopts external current to directly heat the cathode or adopts filament winding heat to heat the emitter in a heat conduction mode. A filament hot cathode comprising a filament 1, an insulator 2, a stem 3, such as shown in fig. 1A; as shown in fig. 1B, the hot wire heating cathode comprises an emitter 4, a bracket 5, ceramic powder 6 and a hot wire 7. In this heating mode, the transverse magnetic field perpendicular to the electron beam direction exists on the cathode surface, which affects the electron movement direction, and results in poor beam quality, and products with small focuses, especially micro-focuses, such as micro Jiao Dianshe line tubes for semiconductor and battery detection, and small focus accelerating tubes for high-precision industrial CT, cannot be satisfied.

In response to the magnetic field generated by such heating currents, electron beam heating and laser heating methods have been proposed, in which the cathode is bombarded with an electron beam or laser to be heated to an operating temperature. An electron beam back heating cathode comprising an emitter 4, an electron beam 8, a filament 1, an insulator 2, a stem 3, as shown for example in fig. 1C; a laser back heated cathode comprising emitter 4, laser 10, window 11, laser 12 is also shown in fig. 1D. The heating mode can effectively eliminate the influence of a transverse magnetic field, so that the beam quality and the service life of a cathode are improved. The electron beam back heating cathode has a relatively complex structure due to the need of providing an additional cathode, an insulation structure and an acceleration power supply for accelerating the heating electron beam. The laser back heating cathode adopts an independent laser, the laser passes through the transmission window to heat the cathode, and the electron gun does not need a heating and insulating structure in the vacuum part, so that the structure is very simple, and the laser back heating cathode is currently used for some electron beam application equipment and scientific research equipment.

The existing laser hot cathode generally adopts emission materials such as W, and as the working temperature of W is about 2700 ℃, the required laser power is very high, the cost is expensive, the laser and the heat dissipation structure are huge, and the product miniaturization requirement cannot be met; meanwhile, due to high cathode temperature, the thermal deformation and interval change of the local structure of the electron gun, particularly the cathode mounting structure and the grid mesh are remarkable, so that the product performance is extremely unstable. FIG. 2A shows a non-deformed cathode assembly structure mainly comprising a grid assembly 13, a heat shield 14, a laser 10, a window 11 and a laser 12, wherein the grid in the grid assembly 13 is not deformed and is in a planar structure; fig. 2B shows the structure of the cathode assembly deformed at high temperature, and it can be seen that the grid mesh in the grid mesh assembly 13 is significantly deformed at high temperature to form an arc surface structure.

To solve the problem of too high a temperature of the laser heated cathode, it is preferable to use a laser heated low operating temperature cathode, such as an oxide cathode, a dispenser cathode, or the like. However, the cathode materials with low operating temperatures are relatively volatile at high temperatures, and in particular, the storage cathode also stores readily vaporizable active materials. In a conventional thermionic heated cathode assembly, the back side of the emitter is sealed with ceramic filled with the thermionic assembly, and the cathode material, even if evaporated, does not contaminate other areas.

In the laser back heating mode, the back of the cathode needs to be irradiated by laser, a cavity for transmitting the laser exists, and the cavity needs to be kept in vacuum, so that the cavity cannot be completely sealed, and needs to be communicated with other vacuum cavities of the device. As shown in fig. 3, in a laser back-heating electron gun and an X-ray source using the electron gun, a cathode assembly 18 and an anode cover 25 are provided inside an insulating member 16, laser light 10 emitted from a laser 12 is irradiated to the back surface of an emitter 4 through a window 11, and electrons generated from the emitter 4 pass through a grid assembly 13 to form an electron beam 8, and enter a lead-out hole in the anode cover. The cathode assembly 18 further includes a cathode structure 19, a heat shield 14, and an exhaust vent 21 is provided in the cathode structure 19. The evaporation of the cathode material from the back side is more pronounced on the laser heated side of the emitter due to the higher temperature than the emitter side. Evaporation of the cathode material not only results in a reduction of the working life of the cathode due to active failure, but also has the following problems: with long-term use, the vapor pollution 20 of the cathode material can diffuse to other areas of the device through the exhaust hole 21, deposit on the surface of metal and insulating parts in a high electric field and cause surface pollution, and insulation breakdown is extremely easy to cause the device to fail; meanwhile, vapor pollution 20 of the cathode material is deposited on the laser transmission window, which directly causes window pollution, reduces the transmission efficiency of laser, causes long-term drift of the actual heating power of the cathode, and is not beneficial to accurate control of electron beam current and stable operation of the laser.

Disclosure of Invention

In order to overcome the problems in the prior art, the utility model provides a cathode laser back heating mechanism, and a long-service-life electron gun and an X-ray source with the cathode laser back heating mechanism.

In order to achieve the above purpose, the present utility model provides the following technical solutions:

the utility model provides a cathode laser back heating mechanism which comprises an emitter, a cathode structural member, a window and a laser, wherein the emitter is arranged on the cathode structural member, the window is connected with the cathode structural member, the emitter, the cathode structural member and the window jointly form a cavity, the cavity is provided with an exhaust hole, the laser is used for generating laser, a shielding cover is arranged on the cathode structural member, the emitter, the cathode structural member and the shielding cover jointly form an inner cavity, the inner cavity is of a closed cavity structure, only a laser through hole is formed in the shielding cover, and the laser penetrates through the window and enters the inner cavity through the laser through hole.

Further, the laser via hole is a right-angle hole or a chamfer hole.

Further, the laser via hole is arranged in the middle of the shielding cover.

Further, the shielding case is a heat conducting structure with a thin center and an outer Zhou Hou.

Further, the back of the emitter is covered with a contamination barrier.

Further, the contamination barrier is a high temperature film layer compatible with the substrate.

Further, the thickness of the pollution barrier is 100nm-1um.

The utility model also provides a long-life electron gun, which comprises a cathode assembly, a grid assembly, an insulating part and an anode cover, wherein the cathode assembly adopts the cathode laser back heating mechanism, the cathode assembly is arranged on one side of the insulating part, the grid assembly is arranged between the cathode assembly and the anode cover, the anode cover is provided with a leading-out hole allowing electron beams to pass through, and the laser is positioned outside the insulating part.

Further, a heat shield is arranged on the outer side of the cathode structural member.

The utility model also provides a long-life X-ray source comprising an anode, an anode cover and the long-life electron gun, wherein the anode is arranged on the other side of the insulating component through the anode cover.

Compared with the prior art, the utility model has the beneficial effects that:

the utility model reduces the evaporation of cathode substances from the evaporation path of pollutants by arranging the small-hole through-focusing-pollution storage structure, and further reduces the evaporation of the cathode substances from the source by arranging the high-temperature pollution barrier structure at the cathode interface, thereby solving the problems of activity failure, insulation breakdown and optical system pollution caused by cathode evaporation.

Drawings

FIG. 1A is a schematic diagram of a filament direct heated cathode; FIG. 1B is a schematic diagram of a filament heated cathode; FIG. 1C is a schematic diagram of the structure of an electron beam back heated cathode; FIG. 1D is a schematic diagram of the structure of an electron beam back heated cathode;

FIG. 2A is a schematic illustration of an undeformed cathode assembly; FIG. 2B is a schematic view of a cathode assembly deformed at elevated temperature;

FIG. 3 is a schematic diagram of vapor pollution of an emitter under laser back heating;

FIG. 4 is a schematic diagram of an electron gun employing a shield to prevent vapor contamination in accordance with the present utility model;

FIG. 5 is a schematic diagram of an electron gun employing a contamination barrier to prevent vapor contamination in accordance with the present utility model;

FIG. 6 is a schematic diagram of an electron gun of the present utility model employing a shield and a contamination barrier to jointly prevent vapor contamination;

FIG. 7 is an enlarged view of a portion of the structure of FIG. 6;

FIG. 8A is a schematic view of a right angle open-cell shield; FIG. 8B is a schematic view of a shield with a chamfered aperture;

fig. 9 is a schematic view of an X-ray source employing an electron gun of the present utility model.

The marks in the figure: 1. a filament; 2. an insulator; 3. a stem; 4. an emitter; 5. a bracket; 6. ceramic powder; 7. a hot wire; 8. an electron beam; 9. a shield; 10. laser; 11. a window; 12. a laser; 13. a grid assembly; 14. a heat shield; 15. an anode; 16. an insulating member; 17. x-rays; 18. a cathode assembly; 19. a cathode structural member; 20. steam pollution; 21. an exhaust hole; 22. steam; 23. pollution deposition; 24. a contamination barrier; 25. an anode cover; 26. and a leading-out hole.

Detailed Description

The utility model is described in further detail below with reference to the accompanying drawings.

Example 1

The cathode laser back heating mechanism of the present embodiment mainly includes an emitter 4, a cathode structural member 19, a window 11, and a laser 12, as shown in fig. 4.

Wherein, the emitter 4 is installed at the upper end of the cathode structural member 19, the window 11 is installed at the lower end of the cathode structural member 19, the emitter 4, the cathode structural member 19 and the window 11 together form a cavity, and in order to make the cavity communicate with other vacuum cavities of the device to keep the vacuum state in the cavity, an exhaust hole 21 is arranged on the cathode structural member 19.

Wherein the cavity is provided with a shielding cover 9 on the cathode structural member 19, the emitter 4, the cathode structural member 19 and the shielding cover 9 together form an inner cavity positioned in the cavity, and the whole inner cavity is a closed cavity except for a laser condensation hole arranged on the shielding cover 9. The laser via is preferably located in the middle of the shield 9. The shape of the hole of the laser via hole is not particularly limited, and can be a right-angle hole (as shown in fig. 8A), a chamfer hole (as shown in fig. 8B) or holes of other shapes, the chamfer hole is preferred in the embodiment, the laser via hole is designed into a chamfer structure, when the size of the small hole is limited, the light passing angle of the small hole can be greatly improved, and the miniaturization and light passing efficiency of the light path are ensured. In the embodiment, the shielding cover preferably adopts a heat conduction design with a thin center and an outer Zhou Hou, so that ablation of the shielding body caused by improper laser focusing can be avoided; the shielding cover can be made of tungsten, tantalum, molybdenum, copper, alloy thereof and the like.

The laser 12 is located outside the cavity, and the laser 10 generated by the laser 12 enters the cavity through the window 11, then converges at the laser via-hole of the shielding cover 9, then enters the inner cavity, and finally irradiates the emitter 4 from the back surface of the emitter 4.

The cathode laser back heating mechanism adopts a small-hole over-focusing and pollution storage structure, so that the diffusion of cathode evaporation pollutants is reduced while the effective heating of laser to the cathode back is ensured. The working principle is as follows: the cathode component is internally provided with a high heat conduction metal cover with an opening, the wider laser forms a strong focused beam through an optical lens, and the beam waist of the beam is consistent with the axial position of the small hole. The laser beam enters the cathode bracket in an overpolymerization mode, and the cathode is heated in a matched size after the beam is expanded. Since the back of the cathode is surrounded by a cavity having only one small hole, most of the contaminated vapor is deposited on the housing and metal cover of the cathode assembly to form a film and stored therein, only a small proportion of the vapor 22 overflows through the small hole and is deposited in the center of the window (i.e., contaminated deposit 23 in fig. 4), thereby greatly reducing contamination of the entire device. Since the vapor has a certain directivity, only the central area of the lens will be contaminated. Since the laser is fed in an overcrowding way, the laser light spot is larger on the window, so that the influence of pollution on the light transmission performance is greatly reduced.

In the embodiment, the small hole is arranged to pass through the focusing-pollution storage structure, so that the evaporation of the cathode substance is reduced from the evaporation path of the pollutant, and the problems of activity failure, insulation breakdown and optical system pollution caused by the evaporation of the cathode can be solved.

Example two

The cathode laser back heating mechanism of the present embodiment is shown in fig. 5, and mainly includes an emitter 4, a cathode structural member 19, a window 11, and a laser 12.

Wherein, the back of the emitter 4 is covered with a pollution barrier 24, and the pollution barrier 24 is a high-temperature film layer prepared on the back of the cathode emitter 4 and used for isolating the cathode from the pollution in vacuum, and the thickness of the pollution barrier is preferably 100nm-1um. The pollution barrier 24 can be made of high-temperature metal such as tungsten and tantalum or high-temperature thin film material such as high-temperature high-heat-conductivity ceramic such as aluminum nitride.

Wherein the laser 12 is located outside the cavity, the laser light 10 generated by the laser 12 enters the cavity through the window 11, irradiates the contamination barrier 24, and the thermal power is conducted to the back of the emitter 4 through the contamination barrier 24.

The cathode laser back heating mechanism adopts a cathode interface high-temperature pollution barrier structure, and the working principle is as follows: on the basis of a traditional emitter, a high-temperature film layer compatible with a matrix material is prepared on one side heated by laser, the emitter is isolated from a vacuum environment while laser heat is transferred to the emitter by the film, and the cathode material is prevented from generating excessive vapor pressure in vacuum at high temperature by physical and chemical combination between the film and the cathode material. On one hand, the structure plays a direct space blocking role, and the role is similar to that of a shielding case which cannot conduct heat; on the other hand, the high-temperature film and the cathode material are tightly physically and chemically combined to form an interface without a vacuum gap, so that the cathode material is prevented from being sublimated rapidly in a vacuum environment at high temperature.

According to the embodiment, the high-temperature pollution barrier structure is arranged at the cathode interface, so that evaporation of cathode substances is reduced from the source, and the problems of activity failure, insulation breakdown and optical system pollution caused by cathode evaporation can be solved.

Example III

The cathode laser back heating mechanism of the present embodiment mainly includes an emitter 4, a cathode structural member 19, a window 11, and a laser 12, as shown in fig. 7.

Wherein, the back of the emitter 4 is covered with a pollution barrier 24, and the pollution barrier 24 is a high-temperature film layer prepared on the back of the cathode emitter 4 and used for isolating the cathode from the pollution in vacuum, and the thickness of the pollution barrier is preferably 100nm-1um. The contamination barrier 24 is preferably made of a high-temperature metal such as tungsten or tantalum or a high-temperature thin film material such as a high-temperature high-heat-conductivity ceramic such as aluminum nitride.

The laser 12 is located outside the cavity, and the laser 10 generated by the laser 12 enters the cavity through the window 11, then converges at the laser via-hole of the shielding cover 9, then enters the inner cavity, and then irradiates the emitter 4 through the pollution barrier 24.

The embodiment adopts a small-hole over-focusing-pollution storage structure and a cathode interface high-temperature pollution barrier structure based on the structure. The evaporation of the cathode material is sequentially reduced from the evaporation path and the source, respectively, so that the problems of activity failure, insulation breakdown and optical system pollution caused by the cathode evaporation can be more effectively avoided compared with the first embodiment and the second embodiment.

Example IV

The present embodiment provides a long-life electron gun having a structure mainly including a cathode assembly 18, a grid assembly 13, and an insulating member 16 as shown in fig. 6.

The cathode assembly 18 is preferably a cathode laser back heating mechanism as described in the third embodiment, the cathode assembly 18 is mounted on one side of the insulating member 16, and the laser 12 is located outside the insulating member 16. The heat shield 14 may also be provided on the outside of the cathode structure 19.

The laser light 10 emitted by the laser 12 is transmitted through the window 11 and is irradiated to the back of the emitter 4 via the laser light converging hole and the pollution barrier 24, and the electron beam 8 generated by the emitter 4 passes through the grid of the grid assembly 13.

In the embodiment, the shielding cover with the center open hole is arranged on the cathode structural member between the back of the cathode and the laser window, the wide-beam spot laser emitted by the laser forms a strong focused beam through the optical lens, and the axial positions of the focal spot and the small hole of the beam are consistent. The laser beam enters the cathode bracket in an overpolymerization mode, and the back of the cathode is heated in a matched size after the beam is expanded. Meanwhile, a high-temperature film layer compatible with the matrix material is prepared on one side heated by laser, the film transfers laser heat to the emitter, the emitter is isolated from a vacuum environment, and the physical and chemical combination between the film and the cathode material is used for avoiding the generation of excessive vapor pressure of the cathode material in vacuum at high temperature.

As shown in fig. 7, the relationship between the contamination storage depth Lc and the laser beam spot Dl, the cathode size Dc, and the distance Ll from the laser beam focusing lens exit to the shield case is: lc=k×dc×ll. Wherein the average temperature control coefficient k=0.8 to 1.2.

Example five

The present embodiment provides an X-ray source, which has a structure as shown in fig. 9, and mainly includes an electron gun and an anode 15. In the tube shown in fig. 9, the electron beam 8 is further accelerated by the electric field between the cathode assembly and the anode cover on the basis of embodiment four, passes through the exit hole and impinges on the anode 15 to emit an exit line 17.

The electron gun preferably adopts the electron gun structure described in the fourth embodiment, the cathode assembly 18 is mounted on one side of the insulating member 16, the anode 15 is mounted on the other side of the insulating member 16 through the anode cover 25, the anode cover 25 is provided with an extraction hole 26 for allowing the electron beam 8 to pass through, the anode 15 is disposed opposite to the cathode assembly 18, the grid of the grid assembly 13 is disposed between the emitter 4 and the anode 15 of the cathode assembly 18, and the laser 12 is disposed outside the insulating member 16. The heat shield 14 may also be provided on the outside of the cathode structure 19.

The laser 10 emitted by the laser 12 passes through the window 11 and irradiates to the back of the emitter 4 through the laser converging hole and the pollution barrier 24, the electron beam 8 generated by the emitter 4 passes through the grid of the grid assembly 13, passes through the extraction hole arranged on the anode cover, and bombards the anode 15 to emit X rays 17.

The above description is only of the preferred embodiments of the present utility model, and is not intended to limit the present utility model. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model should be included in the protection scope of the present utility model.

Claims

1. The cathode laser back heating mechanism is characterized by comprising an emitter, a cathode structural member, a window and a laser, wherein the emitter is arranged on the cathode structural member, the window is connected with the cathode structural member, the emitter, the cathode structural member and the window jointly form a cavity, the cavity is provided with an exhaust hole, the laser is used for generating laser, a shielding cover is arranged on the cathode structural member, the emitter, the cathode structural member and the shielding cover jointly form an inner cavity, the inner cavity is of a closed cavity structure, only a laser through hole is formed in the shielding cover, and the laser penetrates through the window and enters the inner cavity through the laser through hole.

2. The cathode laser backside heating mechanism of claim 1, wherein the laser via is a right angle opening or a chamfer opening.

3. The cathode laser backside heating mechanism of claim 1, wherein the laser via is disposed in the middle of the shield.

4. The cathode laser back heating mechanism of claim 1, wherein the shield is a thermally conductive structure with a central thin, outer Zhou Hou.

5. The cathode laser back heating mechanism of claim 1, wherein the back side of the emitter is covered with a contamination barrier.

6. The cathode laser back heating mechanism of claim 5, wherein the contamination barrier is a high temperature thin film layer compatible with the substrate.

7. The cathode laser back heating mechanism of claim 5, wherein the contamination barrier has a thickness of 100nm-1um.

8. A long-life electron gun, characterized by comprising a cathode assembly, a grid assembly and an insulating part, wherein the cathode assembly adopts the cathode laser back heating mechanism as claimed in any one of claims 1-7, the cathode assembly is arranged on one side of the insulating part, the grid assembly is arranged between the cathode assembly and the anode, and the laser is positioned outside the insulating part.

9. The electron gun of claim 8, wherein the cathode structure is provided with a heat shield on the outside.

10. A long life X-ray source comprising an anode, an anode cover, and the long life electron gun according to claim 8 or 9, wherein the anode is mounted on the other side of the insulating member through the anode cover, and the anode cover is provided with an extraction hole for allowing the electron beam to pass through.