CN111326378A

CN111326378A - Multi-floating grid cathode structure, electron gun, electron accelerator and irradiation device

Info

Publication number: CN111326378A
Application number: CN201811522876.7A
Authority: CN
Inventors: 畅祥云
Original assignee: Shaanxi Liyou Baihui Technology Development Co ltd
Current assignee: Shaanxi Liyou Baihui Technology Development Co ltd
Priority date: 2018-12-13
Filing date: 2018-12-13
Publication date: 2020-06-23
Anticipated expiration: 2038-12-13
Also published as: WO2020118938A1; CN111326378B

Abstract

The invention relates to a multi-floating grid cathode structure, an electron gun, an electron accelerator and an irradiation device. The multi-floating gate cathode structure includes: a cathode for emitting an electron beam; the emission suppression grid is positioned on one side of the cathode emission surface; the first suspension grid anode is arranged at the edge of the first suspension grid, is opposite to the first suspension grid cathode at intervals, and is connected with an external first bias power supply; and the second floating gate is positioned on one side of the first floating gate, which is deviated from the emission suppression gate, the edge of the second floating gate is provided with a second floating gate cathode and a second floating gate anode which is arranged opposite to the second floating gate cathode at intervals, and the second floating gate anode is connected with an external second bias power supply.

Description

Multi-floating grid cathode structure, electron gun, electron accelerator and irradiation device

Technical Field

The present disclosure relates to the field of electron accelerators, and in particular, to a multi-floating-gate cathode structure, an electron gun, an electron accelerator, and an irradiation apparatus.

Background

With the development of science and technology, the application field of the electron accelerator is more and more extensive. The electron linear accelerator is one of the most widely used accelerators, and is widely applied to the aspects of tumor treatment, polymer crosslinking, medical article disinfection, casting flaw detection, food preservation, customs inspection, sterilization and disinsection, isotope production, scientific research, laser weapons and the like. The conventional electron linear accelerator is mainly composed of a direct current section, a beam-converging section and an accelerating section as shown in fig. 1. Since the acceleration section can only accelerate the micro-pulse electron beam consisting of discrete clusters, the lower energy dc electron beam generated by the dc gun must pass through the beam-focusing section to be converted into a micro-pulse electron beam before being accelerated by the following acceleration section. The microwave electron gun accelerator can directly generate electron beams composed of micro pulses, so that the generated electron beams can be directly accelerated by the acceleration section. However, the microwave electron gun cannot work in a high duty ratio state due to the "back-bombardment" effect, has low average power and high cost, and is generally not suitable for irradiation and high-performance accelerator applications. Generally, the average current of the microwave electron gun accelerator is very small, only tens of microamperes, the average power is at most hundreds of watts, and the efficiency is very low.

As shown in fig. 2, a microwave electron gun accelerator is provided in the related art, which can completely eliminate most of the electrons with poor performance in the counter-bombarded electrons and the emitted electrons of the microwave electron gun, so that the microwave electron gun can operate in a continuous wave state, and thus the average current of the microwave electron gun can be greatly increased, that is, the average power can be greatly increased.

However, as shown in fig. 3 and 4, the floating gate cathode structure in the related art makes each beam group of the electron beam emitted from the cathode 10, which constitutes the total beam group, have a divergence angle when leaving the floating gate 30, so that the emittance of the whole beam is increased, or the beam quality is deteriorated, which also makes it difficult to realize a more demanding accelerator application in, for example, medical and military applications. Therefore, there is a need to provide a new technical solution to improve one or more of the problems in the above solutions.

It is noted that this section is intended to provide a background or context to the embodiments of the invention that are recited in the claims. The description herein is not admitted to be prior art by inclusion in this section.

Disclosure of Invention

It is an object of embodiments of the present invention to provide a multi-floating-gate cathode structure, an electron gun, an electron accelerator, and an irradiation apparatus, which overcome one or more of the problems due to the limitations and disadvantages of the related art, at least to some extent.

According to a first aspect of embodiments of the present invention, there is provided a multi-floating gate cathode structure, comprising:

a cathode for emitting an electron beam;

the emission suppression grid is positioned on one side of the cathode emission surface;

the first suspension grid anode is arranged at the edge of the first suspension grid, is opposite to the first suspension grid cathode at intervals, and is connected with an external first bias power supply;

and the second floating gate is positioned on one side of the first floating gate, which is deviated from the emission suppression gate, the edge of the second floating gate is provided with a second floating gate cathode and a second floating gate anode which is arranged opposite to the second floating gate cathode at intervals, and the second floating gate anode is connected with an external second bias power supply.

In an embodiment of the present invention, the magnitude of the second bias voltage provided by the second bias voltage power supply is greater than the magnitude of the first bias voltage provided by the first bias voltage power supply, so that the magnitude of the dc component of the second floating gate is greater than the magnitude of the dc component of the first floating gate.

In an embodiment of the invention, a first filter circuit is connected between the first floating gate anode and the first bias power supply.

In an embodiment of the invention, a second filter circuit is connected between the second floating gate anode and the second bias power supply.

In the embodiment of the invention, a plurality of first holes are arranged on the emission suppression grid, and second holes corresponding to the plurality of first holes are arranged on the first floating grid and the second floating grid.

In an embodiment of the invention, the first holes have a hole diameter of less than 5 mm.

In an embodiment of the present invention, a predetermined gap is formed between the emission-suppressing gate and the cathode, and the predetermined gap is smaller than 1 mm.

In the embodiment of the invention, the gap distance between the first floating gate and the second floating gate is within 5 mm.

According to a second aspect of the embodiments of the present invention, there is provided a microwave electron gun, in which a chamber of the microwave electron gun is provided with the multi-floating-grid cathode structure according to any of the embodiments.

According to a third aspect of the embodiments of the present invention, there is provided an electron accelerator, including the microwave electron gun according to any of the above embodiments, and an accelerator connected to the microwave electron gun.

According to a fourth aspect of the embodiments of the present invention, there is provided an irradiation apparatus including the electron accelerator according to the above embodiments.

The technical scheme provided by the embodiment of the invention can have the following beneficial effects:

in the embodiment of the invention, the bias voltage of each floating gate can be adjusted to ensure that each beam splitting group reaches the minimum divergence angle when leaving the last floating gate, so that the emittance of the total beam group can be greatly reduced, and is about one order of magnitude smaller than the emittance of the total beam group generated by the existing single floating gate scheme, therefore, the quality of the beam generated by the scheme of the embodiment can reach or even exceed the quality of the electron beam generated by the existing photocathode microwave gun, the beam quality becomes better, and the accelerator application in the fields with higher requirements such as medical use, military use and the like is realized.

Drawings

FIG. 1 shows a schematic diagram of a prior art electron linear accelerator;

FIG. 2 shows a schematic diagram of a microwave electron gun accelerator according to the prior art;

FIG. 3 is a schematic diagram of a single floating grid cathode structure of a microwave electron gun according to the prior art;

FIG. 4 shows a schematic of a prior art electron bunch produced by a single floating grid cathode;

FIG. 5 shows a schematic diagram of a double-suspended floating gate cathode structure in an exemplary embodiment of the invention;

FIG. 6 is a schematic diagram of electron bunches generated by a double-suspended floating gate cathode according to an embodiment of the present invention;

figure 7 shows a plot of cluster phase space and divergence contrast for a single floating gate cathode versus a double floating gate cathode.

Detailed Description

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

Furthermore, the drawings are merely schematic illustrations of the invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and thus their repetitive description will be omitted. Some of the block diagrams shown in the figures are functional entities and do not necessarily correspond to physically or logically separate entities.

Emittance is a physical quantity describing the quality of a beam and is related to the minimum size of the beam that can be focused. The smaller the emittance, the smaller the beam spot on which the beam can be focused, i.e., the higher the "brightness" of the beam. The emittance requirements are not high in most irradiation applications, but in some applications there may be a high requirement that the emittance be sufficiently small.

In the existing single floating gate scheme, as shown in fig. 4, each beam cluster (also called a sub-beam cluster) has a divergence angle when leaving the floating gate, so that each beam cluster has a large divergence angle in a phase space as shown in fig. 7, which causes the total beam cluster (also called a total beam cluster) to have a large emittance and poor beam quality.

In order to improve the above problem, the present exemplary embodiment first provides a multi-floating gate cathode structure, which may include a cathode 10, an emission-suppressing gate 20, a first floating gate 30, and a second floating gate 30', as shown in fig. 5. The cathode 10 is configured to emit an electron beam, and the cathode 10 may be a hot cathode, and the hot cathode may be made of a hot cathode material such as lanthanum hexaboride (LaB6), cesium hexaboride (CeB6), a field emission material, and the like, but the hot cathode material is not limited thereto. . The emission-suppressing gate 20 is located at one side of the emission surface of the cathode 10.

The first floating gate 30 is located on a side of the suppression emission gate 20 facing away from the cathode body 10, a first floating gate cathode 31 is disposed at an edge of the first floating gate 30, and a first floating gate anode 32 is disposed opposite to and spaced from the first floating gate cathode 31, and the first floating gate anode 32 is connected to an external first bias power source V1.

Specifically, the first floating gate cathode 31 may be disposed at a circumferential edge of the body of the floating gate 30, for example, the first floating gate cathode 31 may be a separate component disposed at an edge of the floating gate 30, or may be integrally formed with the floating gate 30, which is not limited in this embodiment of the invention. The floating gate anode 32 and the floating gate cathode 31 are spaced apart from each other, and the specific spacing distance can be set by those skilled in the art as needed, which is not limited to this. The first bias voltage source V1 is electrically connected to the floating gate anode 32.

The second floating gate 30 'is located on a side of the first floating gate 30 facing away from the emission suppressing gate 20, a second floating gate cathode 31' is disposed at an edge of the second floating gate 30 ', and a second floating gate anode 32' is disposed opposite to and spaced from the second floating gate cathode 31 ', and the second floating gate anode 32' is connected to an external second bias voltage source V2. Specifically, in an exemplary embodiment, the gap distance between the first and second floating gates 30 and 30' is within 5 mm.

Specifically, the second floating gate cathode 31 ' may be disposed at a circumferential edge of the body of the second floating gate 30 ', for example, the second floating gate cathode 31 ' may be a separate component disposed at the edge of the second floating gate 30 ', or may be integrally formed with the second floating gate 30 ', which is not limited in this embodiment of the present invention. The second floating gate anode 32 'and the second floating gate cathode 31' are spaced apart from each other, and the specific spacing distance can be set by those skilled in the art as needed, which is not limited to this.

The emitter-suppressing gate 20, the first floating body 30 and the second floating body 30' may be supported by a high temperature-resistant insulator (not shown) at the edge to realize "electrical suspension" of the gate body, the insulator being made of a high temperature-resistant insulating material such as a ceramic material or a barium oxide (BeO) material. "suspended" in this context means "electrically suspended" rather than physically suspended with no conductors attached.

In the present embodiment, due to the existence of the first floating gate cathode 31, the electrons intercepted by the first floating gate cathode 31 are discharged onto the first floating gate anode 32 through the first floating gate cathode 31, so that the highest amplitude of the dc component of the first floating gate 30 is controlled by the dc bias of the first floating gate anode 32. Emission control of the electron beam emitted from the cathode 10 can be achieved by controlling the dc component of the first floating gate 30 by controlling the dc bias of the first floating gate anode 32.

Similarly, the control of the dc component of the second floating gate 30 'can be realized similarly to the first floating gate 30, and the amplitude of the dc component of the second floating gate 30' is controlled to be higher than that of the dc component of the first floating gate 30, so as to realize the focus control of the sub-beams emitted from the first floating gate 30.

In one embodiment, the magnitude of the second bias voltage provided by the second bias voltage power supply is greater than the magnitude of the first bias voltage provided by the first bias voltage power supply, such that the magnitude of the dc component of the second floating gate 30' is higher than the magnitude of the dc component of the first floating gate 30. This can achieve better focus control of electrons emitted from the first floating gate 30, and improve beam quality.

Specifically, in one example, the first bias magnitude ranges from tens to thousands of volts, and the second bias magnitude is several volts to hundreds of volts higher than the first bias magnitude. This further improves the beam quality.

Optionally, in the embodiment of the present invention, a first filter circuit 50 is connected between the first floating gate anode 32 and the first bias voltage source V1. A second filter circuit 60 is connected between the second floating gate anode 32' and the second bias voltage source V2. The first filter circuit 50 and the second filter circuit 60, i.e., the filter channels, may be formed by plate capacitors or coaxial capacitors with or without high temperature resistant media. The dielectric material can be ceramic or barium oxide, but is not limited thereto.

In the above embodiment of the present invention, as shown in fig. 6, by adjusting the bias voltage of each floating gate, each beam splitting cluster reaches the minimum divergence angle when leaving the last floating gate, so that the emittance of the total beam cluster is greatly reduced, and is about one order of magnitude smaller than the emittance of the total beam cluster generated by the existing single floating gate scheme, therefore, the quality of the beam generated by the scheme of this embodiment may reach or even exceed the quality of the electron beam generated by the existing photocathode microwave gun, for example, and the beam quality becomes better.

Specifically, referring to fig. 5 to 6, in an embodiment of the invention, a plurality of first holes 201, such as round holes, are formed in the emission suppressing gate, and second holes 301 corresponding to the plurality of first holes 201 are formed in each of the first floating gate 30 and the second floating gate 30'. In an embodiment of the present invention, the diameter of the first hole 201 is smaller than 5 mm. The first floating body 30 and the second floating body 30' are substantially identical in structure.

Specifically, the positions and shapes, such as shapes, of the corresponding first holes 201 and second holes 301 are consistent. The distribution pattern of the plurality of holes is a circle as shown in fig. 6, which is only schematic in fig. 6, and the number of holes may be set as required, which is not limited. The distribution pattern of the plurality of holes may also be in the form of strips, concentric circles or a combination thereof in other embodiments, which are not limited in this embodiment.

Further, optionally, in the embodiment of the present invention, a preset gap is formed between the emission suppressing gate 20 and the cathode 10, and the preset gap is smaller than 1 mm. The predetermined gap in this embodiment is much smaller than the aperture of the suppression emitter gate 20. Since the gap between the suppressor grids is small and the aperture of the suppressor grids is large, the part of the surface of the cathode 10 which is not shielded by the suppressor grids can sense the microwave electric field and emit electrons, so that the average current is improved.

In this embodiment, the bias voltage of each floating gate is adjusted by the same two floating gate systems to achieve a minimum divergence angle for each beam splitting cluster as it leaves the last floating gate 30'. In particular, in the embodiment of the present invention, the bias voltage of the second floating gate 30' is higher, i.e. more negative, which results in a focusing effect on the electron bunch between the two floating gates, thereby counteracting the previously formed divergence angle, so that each bunch is at zero divergence angle when leaving the second floating gate. As shown in fig. 7, the phase space of the beam group generated by the scheme of this embodiment and the total beam group, it is obvious that the emittance of the total beam group generated by the scheme of this embodiment is much smaller than that of the total beam group generated by the scheme of single floating gate. The beam clusters and the total beam cluster generated by the exemplary double-floating-gate scheme, the divergence angle of each beam cluster is corrected to be 0 when each beam cluster leaves the second floating gate 30', so that the total emittance is greatly reduced, and the beam quality is greatly improved.

It should be noted that, as needed, one skilled in the art may use two or more sets of the above-mentioned floating gate system, and the embodiment of the present invention is not limited thereto. The aim of the invention can be achieved by adjusting the bias voltage of each set of floating gates to ensure that each beam splitting cluster reaches the minimum divergence angle when leaving the last floating gate.

According to the scheme provided by the embodiment of the invention, the bias voltage of each floating gate can be adjusted to ensure that each beam splitting group reaches the minimum divergence angle when leaving the last floating gate, so that the emittance of the total beam group can be greatly reduced, and the emittance of the total beam group is about one order of magnitude smaller than that of the total beam group generated by the existing single floating gate scheme, therefore, the quality of the beam generated by the scheme of the embodiment can reach or even exceed that of the electron beam generated by the existing photocathode microwave gun, the beam quality becomes better, and the irradiation application in the fields with higher requirements such as medical use and military use is realized.

The embodiment of the invention also provides a microwave electron gun, wherein the multi-floating-grid cathode structure in any embodiment is arranged in a cavity of the microwave electron gun. For the multi-floating gate cathode structure, reference may be made to the detailed description in the foregoing embodiments, and details are not repeated herein.

The embodiment of the invention also provides an electron accelerator, which comprises the microwave electron gun in any embodiment and an accelerator connected with the microwave electron gun. The electron accelerator may be an electron linear accelerator, but is not limited thereto.

Further, an irradiation device is also provided in the embodiments of the present disclosure, and the irradiation device may include the electron accelerator described in any of the embodiments above. For the electron accelerator, reference is made to the above embodiments, which are not described herein again. The irradiation device may include, but is not limited to, a radiation sterilization device, a medical irradiation device, and the like.

In the microwave electron gun, the electron accelerator and the irradiation device of the embodiment of the invention, the bias voltage of each floating gate can be adjusted to ensure that each beam splitting group reaches the minimum divergence angle when leaving the last floating gate, so that the emittance of the total beam group can be greatly reduced, and the emittance of the total beam group is about one order of magnitude smaller than that of the total beam group generated by the existing single floating gate scheme, therefore, the quality of the beam generated by the scheme of the embodiment can reach or even exceed that of the electron beam generated by the existing photocathode microwave gun, the beam quality becomes better, and the accelerator application in the fields with higher requirements such as medical use and military use can be realized.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples described in this specification can be combined and combined by those skilled in the art.

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

Claims

1. A multi-floating gate cathode structure, comprising:

a cathode for emitting an electron beam;

2. The multi-floating-gate cathode structure of claim 1, wherein the magnitude of the second bias voltage provided by the second bias voltage power supply is greater than the magnitude of the first bias voltage provided by the first bias voltage power supply, such that the magnitude of the dc component of the second floating gate is greater than the magnitude of the dc component of the first floating gate.

3. The multi-floating-gate cathode structure of claim 2, wherein a first filter circuit is connected between the first floating-gate anode and a first bias power supply.

4. The multi-floating-gate cathode structure of claim 2, wherein a second filter circuit is connected between the second floating-gate anode and a second bias power supply.

5. The multi-floating-gate cathode structure according to any one of claims 1 to 4, wherein a plurality of first holes are formed in the emission-suppressing gate, and second holes corresponding to the plurality of first holes are formed in each of the first floating gate and the second floating gate.

6. The multi-floating-gate cathode structure according to claim 5, wherein the first holes have a hole diameter of less than 5 mm.

7. The multi-floating-gate cathode structure according to claim 5, wherein the suppressor emitter gate and the cathode have a predetermined gap therebetween, and the predetermined gap is less than 1 mm.

8. The multi-floating gate cathode structure according to claim 5, wherein the gap distance between the first floating gate and the second floating gate is within 5 mm.

9. A microwave electron gun, wherein a multi-floating-grid cathode structure as claimed in any one of claims 1 to 8 is disposed in a cavity of the microwave electron gun.

10. An electron accelerator comprising the microwave electron gun of claim 9, and an accelerator connected to the microwave electron gun.

11. An irradiation apparatus comprising the electron accelerator according to claim 10.