Electron gun

Abstract

An electron gun may include a cathode having an emission surface configured to emit electrons. The cathode may include a through-hole through the emission surface, the through-hole configured to allow backflow electrons of electrons emitted by the cathode to pass through. The electron gun may also include an anode configured to attract the electrons emitted by the cathode from the cathode to the anode and focus the electrons emitted by the cathode into an electron beam.

Description

Division Case Explanation

[0001] This application is a divisional application of a patent application for invention with international application number PCT / CN2020 / 096230, international filing date of June 15, 2020, date of entry into the Chinese national phase of December 13, 2022, national application number 202080101891.3, and invention title "Electron Gun". Technical Field

[0002] This application relates to an electron gun, and particularly to an electron gun including a hollow cathode and a grid structure, the grid structure being configured to reduce or eliminate backflow electrons on the cathode. Background Art

[0003] There are two types of electron guns. The first type of electron gun is a diode electron gun, which includes two electrodes, such as a cathode and an anode. The second type of electron gun is a triode electron gun, which includes three electrodes, such as a cathode, an anode, and a grid. Summary of the Invention

[0004] According to one aspect of this specification, an electron gun may include a cathode having an emission surface configured to emit electrons, the cathode including a through hole passing through the emission surface, the through hole being configured to allow backflow electrons of the electrons emitted by the emission surface to pass through; an anode configured to attract the electrons emitted by the emission surface from the cathode to the anode and focus the electrons into an electron beam; and a grid structure configured to facilitate focusing of the electrons into the electron beam, the position of the grid structure corresponding to the through hole.

[0005] In some embodiments, at least one of the cathode, the through hole, the grid structure, or the anode is centered on the common axis of the electron gun.

[0006] In some embodiments, at least a portion of the projection of the grid structure along the common axis is located within the cross-section of the through hole, the cross-section being perpendicular to the common axis.

[0007] In some embodiments, the voltage of the grid structure is the same as the voltage of the cathode.

[0008] In some embodiments, the grid structure includes two or more first mesh holes, and the backflow electrons pass through the two or more first mesh holes.

[0009] In some embodiments, the two or more first mesh holes are related to the counting of the backflow electrons passing through the grid structure and the focusing of the electrons emitted from the cathode.

[0010] In some embodiments, the grid structure is in contact with the cathode.

[0011] In some embodiments, there is a gap between the grid structure and the cathode.

[0012] In some embodiments, the grid structure is supported by a grid support.

[0013] In some embodiments, the cathode includes a first material configured to facilitate the emission of electrons from the cathode by reducing the work function of the cathode.

[0014] In some embodiments, the grid structure includes a second material that chemically reacts with the first material.

[0015] In some embodiments, the first material includes barium (Ba), and the second material includes a transition metal, and the transition metal includes at least one of zirconium (Zr) or hafnium (Hf).

[0016] In some embodiments, the second material is configured to prevent the grid structure from emitting electrons due to the impact of at least a portion of the backflow electrons on the grid structure.

[0017] In some embodiments, the electron gun further includes a grid configured to control the flow of electrons emitted from the cathode toward the anode, and the grid is located between the cathode and the anode.

[0018] In some embodiments, the grid is centered on the common axis of the electron gun.

[0019] In some embodiments, the grid includes two or more second mesh holes configured to allow the electrons emitted from the cathode or the backflow electrons to pass through.

[0020] In some embodiments, the two or more second mesh holes include a central mesh hole corresponding to the through hole, and the central mesh hole is configured to allow the backflow electrons to pass through and prevent the backflow electrons from impacting the grid, and the central mesh hole is centered on the common axis.

[0021] In some embodiments, the grid includes a third material that chemically reacts with the first material.

[0022] In some embodiments, the grid structure is located at a fixed position between the cathode and the grid.

[0023] In some embodiments, the position of the grid structure is adjustable along the common axis between the cathode and the grid.

[0024] In some embodiments, the electron gun further includes an energy source configured to supply energy to the cathode, so that the cathode emits the electrons.

[0025] In some embodiments, the electron gun further includes an electron receiving device configured to receive the reflux electrons passing through the through hole of the cathode.

[0026] In some embodiments, the electron gun further includes a focusing electrode for focusing the electrons emitted by the cathode into the electron beam.

[0027] Some additional features of the present application can be illustrated in the following description. Through the study of the following description and the corresponding drawings, or the understanding of the production or operation of the embodiments, some additional features of the present application are obvious to those of ordinary skill in the art. The features of the present application can be realized and achieved through the practice or use of the methods, means, and combinations of various aspects of the specific embodiments described below. Description of the Drawings

[0028] This specification will be further described in the form of exemplary embodiments. These exemplary embodiments will be described in detail through the drawings. These are non-limiting exemplary embodiments, in which the same numbers in each figure represent the same structures, where:

[0029] Figure 1 and Figure 2 is a schematic cross-sectional view of an exemplary triode electron gun shown in some embodiments of this specification;

[0030] Figure 3 is a schematic view of an exemplary grid structure shown in some embodiments of this specification. Detailed Description of the Embodiments

[0031] In order to more clearly illustrate the technical solutions of the embodiments of this specification, the drawings required for use in the description of the embodiments will be briefly introduced below. However, those skilled in the art should understand that this specification can be implemented without these details. In other cases, in order to avoid unnecessarily obscuring some aspects of this specification, well-known methods, procedures, systems, components, and / or circuits have been described in more detail. For those of ordinary skill in the art, it is obvious that various changes can be made to the disclosed embodiments, and without departing from the principles and scope of this specification, the general principles defined in this specification can be applied to other embodiments and application scenarios. Therefore, this specification is not limited to the shown embodiments, but conforms to the broadest scope consistent with the patent scope of the specification.

[0032] The terms used in this specification are for the purpose of describing particular exemplary embodiments only and are not intended to limit the scope of this specification. As used in this specification and the appended claims, unless the context clearly dictates otherwise, the words "a," "an," "the," and / or "said" are not intended to refer to the singular only and may include the plural. It should be understood that the terms "comprising" and "including" as used in this specification are merely indicative of the features, wholes, steps, operations, elements, and / or components that have been expressly identified, and do not preclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or any combination thereof.

[0033] Note that the terms "system," "apparatus," "unit," and / or "module" as used in this specification are a means of distinguishing between different components, elements, parts, portions, or assemblies at different levels. However, if other expressions can achieve the same purpose, the said terms may be replaced by other expressions.

[0034] Generally, the words "system," "apparatus," "unit," and / or "module" as used in this specification refer to the logic embodied in hardware or firmware, or to a collection of software instructions. The modules, units, or blocks described herein may be implemented as software and / or hardware and may be stored in any type of non-transitory computer-readable medium or another storage device. In some embodiments, the software systems, apparatuses, units, and / or modules may be compiled and linked into an executable program. It should be understood that software modules may be called from other systems, apparatuses, units, modules, and / or from themselves, and / or may be called in response to detected events or interrupts. The software systems, apparatuses, units, and / or modules configured to execute on a computing device may be provided on a computer-readable medium, such as a compact disc, digital video disc, flash drive, disk, or any other tangible medium, or as a digital download (and may initially be stored in a compressed or installable format that requires installation, decompression, or decryption before execution). The software code may be stored, in part or in whole, in the storage device of the computing device performing the operations and applied in the operation of the computing device. The software instructions may be embedded in firmware, such as an EPROM. Further, the hardware modules / units / blocks may include connected logic components, such as gates, flip-flops, and / or programmable units, such as a programmable gate array or a processor. The systems, apparatuses, units, and / or modules or computing device functions described herein may be implemented as software modules, units, or blocks, but may be represented by hardware or firmware. Generally, the systems, apparatuses, units, and / or modules described herein refer to logical systems, apparatuses, units, and / or modules, which may be combined with other systems, apparatuses, units, and / or modules or divided into subsystems, sub-apparatuses, sub-units, and / or sub-modules, regardless of their physical organization or storage device.

[0035] It should be understood that when a system, device, unit, and / or module is referred to as being "located at", "connected to", or "coupled to" another system, device, unit, and / or module, unless otherwise explicitly stated in the context, these systems, devices, units, and / or modules can be directly located at, connected to, or coupled to the other system, device, unit, and / or module, or there may be intermediate systems, devices, units, and / or modules. In this specification, the term "and / or" can include any one or a combination of at least one of the related listed items.

[0036] After considering the description of the accompanying drawings which are part of this specification, the features, characteristics, and operating methods described in this specification, the functions of the related structural elements, the combination of various components, and the economy of manufacture become more apparent. However, it should be understood that the accompanying drawings are only for the purpose of illustration and description and are not intended to limit the scope in this specification. It should be understood that the accompanying drawings are not drawn to scale.

[0037] A linear particle accelerator, or a klystron, uses an electron beam source, usually referred to as an electron gun. For example, in some cases, when an electron gun is used as the electron source in an electron linear accelerator, a part of the electrons output from the electron gun (referred to as return electrons) may return to the electron gun. The return electrons may have an adverse effect on the cathode of the electron gun, such as causing the cathode to overheat, which in turn may shorten the life of the cathode, reduce the performance of the cathode, etc. Therefore, it is desirable to provide an electron gun to mitigate or solve the influence of the return electrons on the cathode.

[0038] One aspect of this specification relates to an electron gun including a hollow cathode. The electron gun may include a cathode and an anode. Optionally, the electron gun may further include a grid. The cathode may include a through hole configured to allow the return electrons to pass through. The return electrons can pass through the through hole instead of hitting the cathode, thus avoiding overheating of the cathode. The electron gun may further include a grid structure configured to promote the focusing of the electrons emitted from the cathode. The grid structure may be located between the cathode and the anode. The grid structure may be located at a position corresponding to the through hole. At least a part of the projection of the grid structure along the common axis may be located within the cross section of the through hole, and the cross section is perpendicular to the common axis. Due to the presence of the through hole, there will be a discontinuity in the emission surface of the cathode. The electric field formed between the cathode and the anode based on the discontinuity will focus the electrons emitted from the cathode into an electron beam, but the convergence of this electron beam is relatively poor. By using the grid structure, the electric field between the cathode and the anode can focus the electrons emitted from the cathode into an electron beam, and this electron beam has better convergence compared to the case without the grid structure.

[0039] Figure 1 and Figure 2It is a schematic cross-sectional view of an exemplary triode electron gun shown in some embodiments of this specification. The electron gun 100 may include a cathode 110, a grid structure (e.g., the grid structure 121 in Figure 1 or the grid structure 122 in Figure 2 ), a grid electrode 130, and an anode 140. In some embodiments, the cathode 110, the grid electrode 130, and the anode 140 may be centered on the common axis 160 of the electron gun 100. In some embodiments, the electron gun 100 may further include at least one of a focusing electrode 150, an energy source (not shown), and a receiving device (not shown). In some embodiments, the focusing electrode 150 may be centered on the common axis 160. In some embodiments, along the emission direction of the electrons emitted from the cathode 110, the anode 140 may be located downstream of the cathode 110. The grid electrode 130 may be located between the cathode 110 and the anode 140. The focusing electrode 150 may be located between the grid electrode 130 and the anode 140.

[0040] In some embodiments, Figure 1 the X-axis, Y-axis, and Z-axis shown in Figure 1 may form an orthogonal coordinate system. As shown, the Z-axis may be parallel to the common axis 160. The direction from the cathode 110 to the anode 140 may be the positive direction of the Z-axis. The positive direction of the Y-axis may be from the right side to the left side of the electron gun 100 as seen from the negative direction of the Z-axis. In Figure 1 for ease of illustration, the X-axis may be represented as perpendicular to the paper. The positive direction of the X-axis may be from the upper side to the lower side of the electron gun 100 as seen from the negative direction of the Z-axis. Figure 2 The X-axis, Y-axis, and Z-axis shown in Figure 1 are similar to the X-axis, Y-axis, and Z-axis in Figure 1 . Figure 1 and Figure 2 show a cross-section of the electron gun 100 parallel to the Y-Z plane.

[0041] The cathode 110 may include an emission surface 112 configured to emit electrons. In some embodiments, the emission surface 112 may face the anode 140. The emission surface 112 may be a flat surface or a curved surface (e.g., a concave surface as shown in Figure 1 ). In some embodiments, the emission surface 112 may be centered on the common axis 160.

[0042] When the temperature of a metal increases, the kinetic energy of the electrons in the metal may increase accordingly. When the temperature rises to a certain value, a large number of electrons will overcome the work function of the metal and escape from the metal. This phenomenon is called thermionic emission. In some embodiments, the cathode 110 may be hot enough to emit electrons from the emission surface 112 through thermionic emission.

[0043] In some embodiments, the cathode 110 (e.g., the emission surface 112) may include a metallic material such as tungsten (W) and its alloys. By heating the cathode 110, the outer electrons of the metallic material atoms can be excited by a specific energy. The excited electrons can overcome the work function of the metallic material and break free from the orbital bondage, becoming free electrons emitted from the cathode 110 (e.g., the emission surface 112). The energy required for the electrons to escape from the cathode 110 may be referred to as the work function of the cathode 110. In some embodiments, the cathode 110 may further include a first material such as barium (Ba), which is configured to facilitate the emission of electrons from the cathode 110 by reducing the work function of the cathode 110. In some embodiments, the cathode 110 may be impregnated with the first material.

[0044] The electrons emitted from the cathode 110 (also referred to as emitted electrons) can fly out of the electron gun 100 under the attraction of the anode 140. In some cases, a portion of the emitted electrons (referred to as reflux electrons) may return to the electron gun 100. For example, when the electron gun 100 is used as an electron source of an electron linear accelerator, the electron linear accelerator may be connected to the anode 140. The emitted electrons can enter the electron linear accelerator from the electron gun 100 through the anode 140. Since the frequency at which the emitted electrons are injected from the electron gun 100 into the electron linear accelerator is not synchronized with the frequency of the acceleration field (e.g., an electric field or an electromagnetic field) used to accelerate the emitted electrons and applied to the electron linear accelerator, some of the emitted electrons are accelerated in a direction opposite to the emission direction of the electrons emitted from the cathode 110, thus returning to the electron gun 100. It should be noted that the electron gun provided in the present disclosure can also be used to reduce or eliminate reflux electrons caused by other reasons.

[0045] Assuming the cathode 110 is solid, the reflux electrons will strike the cathode 110, for example, in the region of the emission surface 112 centered on the common axis 160. The reflux electrons striking the cathode 110 may cause the temperature of the cathode 110 to rise, resulting in overheating of the cathode 110. The overheating of the cathode 110 may cause many problems. For example, the evaporation rate of the first material in the cathode 110 may increase with the increase in temperature. Therefore, the overheating of the cathode 110 may accelerate the evaporation rate of the first material, thereby reducing the lifespan of the cathode 110. For another example, the evaporated first material may deposit on the inner wall of the electron linear accelerator. The deposited first material can reduce the work function of the inner wall of the electron linear accelerator and correspondingly cause some electrons to be emitted from the inner wall of the electron linear accelerator. Under the action of the internal electric field gradient of the electron linear accelerator, the electrons emitted from the inner wall of the electron linear accelerator may form a "dark current", consuming the power of the electron linear accelerator.

[0046] In some embodiments of the present invention, as Figure 1As shown, the cathode 110 can be a hollow cathode including a first through-hole 114 passing through the emission surface 112 and configured to allow backflow electrons that emit electrons to pass through. The first through-hole 114 can extend along a common axis 160 and pass through the cathode 110. The backflow electrons can pass through the first through-hole 114 instead of hitting the cathode 110, thus preventing the backflow electrons from overheating the cathode 110.

[0047] In some embodiments, the position of the first through-hole 114 in the cathode 110, the size and shape of the first through-hole 114 can be configured so that most (e.g., at least 90%) of the backflow electrons that emit electrons pass through the first through-hole 114 instead of hitting the cathode 110. For example, the first through-hole 114 can be centered on the common axis 160. As another example, the first through-hole 114 can be a cylinder with a cross-section that is a circle parallel to the X-Y plane.

[0048] Due to the different voltages on the components (such as the cathode 110, the grid 130, the focusing electrode 150, the anode 140, etc.) in the electron gun 100, an electric field including curved equipotential surfaces and / or electric field lines can be formed between the cathode 110 and the anode 140, which can change the trajectory of the emitted electrons from the cathode 110 to the anode 140, resulting in the convergence and / or divergence of the emitted electrons, thereby achieving the focusing of the emitted electrons into an electron beam. The emitted electrons can leave the electron gun 100 in the form of an electron beam.

[0049] Based on the electric field between the cathode 110 and the anode 140 formed by the discontinuous emission surface 112 having holes corresponding to the first through-hole 114, the emitted electrons can be focused into an electron beam, but the convergence of this electron beam is relatively poor. To improve the focusing of the emitted electrons, a grid structure can be applied in the electron gun 100.

[0050] The grid structure can be configured to facilitate the focusing of the emitted electrons. In some embodiments, the grid structure can be located between the cathode 110 and the anode 140. In some embodiments, the position of the grid structure can correspond to the first through-hole 114. In some embodiments, the grid structure can be connected to the first through-hole 114. For example, the first through-hole 114 and the grid structure can be centered on the common axis 160. In some embodiments, at least a portion of the projection of the grid structure along the negative Z-axis direction can be located within the cross-section parallel to the X-Y plane of the first through-hole 114. For example, the entire projection of the grid structure along the negative Z-axis direction can be located within the cross-section parallel to the X-Y plane of the first through-hole 114. As another example, the projection of the first portion of the grid structure along the negative Z-axis direction can be located within the cross-section parallel to the X-Y plane of the first through-hole 114, while the projection of the second portion of the grid structure along the negative Z-axis direction can be located outside the cross-section parallel to the X-Y plane of the first through-hole 114.

[0051] The grid structure can improve the poor convergence caused by the discontinuous emission surface 112 having holes corresponding to the first through holes 114. Through the grid structure, the electric field between the cathode 110 and the anode 140 can focus the emitted electrons into an electron beam, which has better convergence compared to the case without the grid structure.

[0052] In some embodiments, the grid structure may include a first grid frame and two or more first mesh holes through which the reflux electrons of the emitted electrons can pass. The first grid frame may include multiple crossing lines (e.g., wires). The first grid frame may define the two or more first mesh holes.

[0053] By way of example only, Figure 3 is a schematic diagram of an exemplary grid structure shown in some embodiments of this specification. Figure 3 Shows in Figure 1 or Figure 2 a view of the grid structure 300 seen from the positive or negative direction of the Z-axis. As shown, the grid structure 300 may include a first grid frame 310 and two or more first mesh holes (e.g., mesh holes 320) through which the reflux electrons can pass. The first grid frame may include multiple crossing lines (e.g., wires).

[0054] In some embodiments, the grid pattern of the grid structure determined based on the first grid frame and two or more first mesh holes may indicate the size, shape of each of the two or more first mesh holes, the number of the two or more first mesh holes, the total area of the two or more first mesh holes, the thickness of the crossing lines forming the first grid frame, the density of the two or more first mesh holes in the grid structure (e.g., the number of first mesh holes per unit area in the grid structure), etc., or any combination thereof. In some embodiments, the larger the size of the two or more first mesh holes, the more reflux electrons may pass through the grid structure, but the poorer the focusing performance of the grid structure. The grid pattern of the grid structure can be configured so that most (e.g., at least 60%, at least 70%, at least 80%, at least 90%, etc.) of the reflux electrons can pass through the grid structure instead of hitting the first grid frame of the grid structure, and the focusing of the emitted electrons can form an electron beam with better convergence.

[0055] In some embodiments, the grid structure may have the same voltage as the cathode 110 to suppress electron emission from the inner wall 116 of the first through hole 114. In some embodiments, when the cathode 110 is heated, to prevent thermionic emission of the grid structure, the grid structure may be thermally isolated from the cathode 110, and / or the work function of the grid structure may be higher than that of the cathode 110.

[0056] In some embodiments, if the evaporated first material from the cathode 110 is deposited on the grid structure, the deposited first material can reduce the work function of the grid structure. The backflow electrons impinging on the first grid frame of the grid structure may increase the temperature of the grid structure and cause some electrons to be emitted from the grid structure. The grid structure of the electron gun 100 shown in the embodiments of this specification may include a second material that chemically reacts with the first material. In some embodiments, if the first material includes Ba, the second material may include a transition metal, and the transition metal includes at least one of zirconium (Zr) or hafnium (Hf) that chemically reacts with Ba. The second material can be used to reduce or eliminate the deposition of the first material on the grid structure and / or the electron emission caused by the impingement of at least a portion of the backflow electrons on the grid structure.

[0057] In some embodiments, the grid structure (e.g., Figure 1 the grid structure 121 shown in Figure 2 may be in contact with the cathode 110. For example, the grid structure can be welded to the cathode 110. In some embodiments, there may be a gap between the grid structure and the cathode 110. For example, as Figure 2 shown, there can be a gap 170 between the grid structure 122 and the cathode 110. In some embodiments, the grid structure can be supported by a grid support. For example, as

[0058] shown, the grid structure 122 can be supported by a grid support 180. The grid support 180 can have the same voltage as the cathode 110. In some embodiments, to prevent thermionic emission of the grid support 180 when the cathode 110 is heated, the grid support 180 can be thermally isolated from the cathode 110, and / or the work function of the grid support 180 can be higher than that of the cathode 110. In some embodiments, to reduce or avoid the deposition of the first material on the grid support 180 and / or the electron emission from the grid support 180 due to the impingement of at least a portion of the backflow electrons on the grid support 180, the grid support 180 can include a material that chemically reacts with the first material. This material can be similar to the second material of the grid structure described elsewhere in this specification and will not be elaborated here.

[0058] In some embodiments, the grid structure can be located between the cathode 110 and the anode 140. In some embodiments, the grid structure can be closer to the cathode 110 relative to the anode 140. In some embodiments, the grid structure can be located at a fixed position between the cathode 110 and the anode 140. In some embodiments, the position of the grid structure can be adjustable, e.g., adjusted between the cathode 110 and the anode 140 along the common axis 160.

[0059] In some embodiments, the grid structure may be located between the cathode 110 and the grid electrode 130. In some embodiments, the grid structure may be located at a fixed position between the cathode 110 and the grid electrode 130. In some embodiments, the position of the grid structure may be adjustable, e.g., adjusted between the cathode 110 and the grid electrode 130 along the common axis 160.

[0060] The grid electrode 130 may be configured to control the flow of emitted electrons from the cathode 110 to the anode 140. For example, if the grid electrode 130 maintains a negative voltage relative to the cathode 110, the electric field between the cathode 110 and the grid electrode 130 may be a decelerating electric field for the emitted electrons. The emitted electrons may escape from the cathode 110 with an initial velocity. Due to the decelerating electric field between the grid electrode 130 and the cathode 110, the electrons with a relatively small initial velocity may return to the cathode 110, and the electrons with a relatively large initial velocity move to the anode 140. Therefore, the number of electrons emitted from the cathode 110 to the anode 140 can be controlled by adjusting the voltage of the grid electrode 130. When the grid electrode 130 maintains a sufficiently high negative voltage relative to the cathode 110, all the emitted electrons can be driven back to the cathode 110, such that no electrons move to the anode 140. If the voltage of the grid electrode 130 is positive relative to the cathode 110, an accelerating electric field for the emitted electrons is formed between the grid electrode 130 and the cathode 110, and the emitted electrons will move towards the anode 140.

[0061] In some embodiments, the grid electrode 130 may provide the same voltage as the focusing electrode 150. In some embodiments, if the emission surface 112 is concave, the grid electrode 130 may include a concave surface facing the anode 140. The concave surface of the grid electrode 130 and the emission surface 112 may respectively correspond to two concentric circles.

[0062] In some embodiments, the grid electrode 130 may include a second grid frame and two or more second mesh holes configured to allow the electrons emitted from the cathode and moving to the anode 140 to pass through, and / or allow the reflux electrons to pass through and reach the cathode 110. The second grid frame may include a plurality of intersecting lines (e.g., wires). The two or more second mesh holes may be defined by the second grid frame.

[0063] In some embodiments, the grid pattern of the grid electrode 130 determined based on the second grid frame and the two or more second mesh holes may indicate the size, shape of each of the two or more second mesh holes, the number of the two or more second mesh holes, the total area of the two or more second mesh holes, the thickness of the intersecting lines forming the second grid frame, the density of the two or more second mesh holes in the grid electrode 130 (e.g., the number of second mesh holes per unit area in the grid electrode 130), etc., or any combination thereof.

[0064] In some embodiments, a part of the grid pattern of the gate 130 corresponding to the grid structure may be the same as or different from the grid pattern of the grid structure. The part of the gate 130 corresponding to the grid structure may refer to an area on the gate 130 covered by the projection of the grid structure on the gate 130 in the positive Z-axis direction.

[0065] In some embodiments, if the evaporated first material from the cathode 110 is deposited on the gate 130, the deposited first material may reduce the work function of the gate 130. The reflux electrons hitting the second grid frame of the gate 130 may cause the temperature of the gate 130 to increase, enabling the gate 130 to emit electrons. When the gate 130 is configured to reduce or eliminate the number of electrons moving to the anode 140, it means that few or no electrons need to be output from the electron gun 100. In this case, since the anode 140 maintains a positive voltage relative to the gate 130, the electrons emitted from the gate 130 based on the first material deposited on the gate 130 and the reflux electrons hitting the gate 130 may still be attracted by the anode 140 and fly out of the electron gun 100, resulting in the output of unwanted electrons from the electron gun 100.

[0066] The first through-hole 114 can alleviate or solve the above problems of the gate 130 by avoiding or reducing the overheating of the cathode 110 caused by the reflux electrons hitting the cathode 110.

[0067] In some embodiments, to further alleviate or solve the above problems of the gate 130, two or more second mesh holes of the gate 130 may include a central mesh hole 132 corresponding to the first through-hole 114, and the central mesh hole 132 is configured to allow the reflux electrons to pass through and prevent the reflux electrons from hitting the gate 130. In some embodiments, the central mesh hole 132 may be coaxial with the first through-hole 144. For example, the first through-hole 144 and the gate 130 may be centered on a common axis 160. The shape of the central mesh hole 132 may be the same as or similar to the cross-sectional shape of the first through-hole 114 parallel to the X-Y plane, and the size of the central mesh hole 132 may be equal to, larger than, or smaller than the cross-sectional size of the first through-hole 114. Alternatively, the gate 130 may include a third material that chemically reacts with the first material. In some embodiments, if the first material includes Ba, the third material may include a transition metal, which includes at least one of zirconium (Zr) or hafnium (Hf) that chemically reacts with Ba. The third material may be configured to reduce or avoid the deposition of the first material on the gate 130 and / or the emission of electrons from the gate 130 due to at least a part of the reflux electrons hitting the electrode 130.

[0068] In some embodiments, when the projection of the entire grid structure in the Z-axis direction extends beyond the first through-hole 114, the grid structure can intercept the backflow electrons that would otherwise be intercepted by the gate 130, thereby reducing the pressure on the gate 130 to intercept the backflow electrons.

[0069] The anode 140 can be configured to attract the emitted electrons from the cathode 110 to the anode 140 by maintaining a positive voltage relative to the cathode 110. In some embodiments, the anode 140 can be further configured to focus the emitted electrons into an electron beam. In some embodiments, the anode 140 can include a second through-hole 190 through which the emitted electrons can leave the electron gun 100. In some embodiments, the second through-hole 190 can be centered on the common axis 160.

[0070] The focusing electrode 150 can be configured to focus the emitted electrons into an electron beam.

[0071] The energy source can be configured to supply energy (e.g., thermal energy or electrical energy) to the cathode 110 such that electrons can be emitted from the cathode 110 (e.g., thermionic emission).

[0072] The electron receiving device can be configured to receive the backflow electrons of the emitted electrons passing through the first through-hole 114 of the cathode 110. In some embodiments, the electron receiving device can include a metal material electrically connected to the ground. In some embodiments, the electron receiving device can be located upstream of the cathode 110 in the positive Z-axis direction.

[0073] In some embodiments, the cathode 110 having the first through-hole 114 and the grid structure shown in this description can also be applied to a diode electron gun to alleviate or solve the overheating of the cathode caused by the impact of backflow electrons on the cathode.

[0074] It should be noted that the above description is provided for illustrative purposes only and is not intended to limit the scope of this specification. For those of ordinary skill in the art, various changes and modifications can be made based on the description of this specification. However, these changes and modifications do not depart from the scope of this specification.

[0075] The basic concepts have been described above. Obviously, for those of ordinary skill in the art after reading this application, the above disclosure is only an example and does not constitute a limitation to this application. Although not explicitly stated here, those of ordinary skill in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are proposed in this application, so such modifications, improvements, and corrections still fall within the spirit and scope of the exemplary embodiments of this application.

[0076] Meanwhile, this application uses specific terms to describe the embodiments of this application. For example, "one embodiment", "an embodiment", and / or "some embodiments" mean a certain feature, structure, or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that "one embodiment", "an embodiment", and / or "some embodiments" mentioned two or more times at different positions in this application do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application can be appropriately combined.

[0077] In addition, those of ordinary skill in the art can understand that various aspects of this application can be illustrated and described by several patentable types or situations, including any new and useful process, machine, product, or composition of matter, or any new and useful improvement thereof. Accordingly, various aspects of this application can be executed entirely by hardware, entirely by software (including firmware, resident software, microcode, etc.), or by a combination of hardware and software. The above hardware or software can all be referred to as "data blocks", "modules", "engines", "units", "components", or "systems". In addition, various aspects of this application can take the form of a computer program product embodied in one or more computer-readable media, in which computer-readable program code is included.

[0078] In addition, unless clearly stated in the claims, the order of the processing elements and sequences, the use of numerical letters, or the use of other names in this application are not used to limit the order of the processes and methods of this application. Although some currently considered useful embodiments of the invention are discussed through various examples in the above disclosure, it should be understood that such details only serve the purpose of illustration, and the appended claims are not limited to the disclosed embodiments. On the contrary, the claims are intended to cover all modifications and equivalent combinations that conform to the essence and scope of the embodiments of this application. For example, although the system components described above can be implemented by hardware devices, they can also be implemented only through a software solution, such as installing the described system on an existing server or mobile device.

[0079] Similarly, it should be noted that, in order to simplify the expression of the disclosure of this application and thus help the understanding of one or more embodiments of the invention, in the previous description of the embodiments of this application, sometimes multiple features are merged into one embodiment, drawing, or description thereof. However, this disclosure method does not mean that the features required by the subject matter of this application are more than those mentioned in the claims. In fact, the features of the embodiments are less than all the features of the individual embodiments disclosed above.

Claims

1. An electron gun, characterized in that, Comprising: A cathode having an emission surface configured to emit electrons, the cathode including a through-hole passing through the emission surface, the through-hole being configured to allow backflow electrons of the electrons emitted by the emission surface to pass through; An anode configured to attract the electrons emitted by the emission surface from the cathode to the anode and focus the electrons into an electron beam; And A grid configured to control the flow of the electrons emitted from the cathode towards the anode, the grid being located between the cathode and the anode.

2. The electron gun according to claim 1, characterized in that, At least one of the cathode, the through-hole or the anode is centered on the common axis of the electron gun.

3. The electron gun according to claim 1, characterized in that, The grid is centered on the common axis of the electron gun.

4. The electron gun according to claim 1, characterized in that, The grid includes two or more second mesh holes configured to allow the electrons or the backflow electrons emitted from the cathode to pass through.

5. The electron gun according to claim 1, characterized in that, The two or more second mesh holes include a central mesh hole corresponding to the through-hole, the central mesh hole being configured to allow the backflow electrons to pass through and prevent the backflow electrons from impacting the grid, the central mesh hole being centered on the common axis.

6. The electron gun according to claim 1, characterized in that, The grid includes a third material that chemically reacts with a first material included in the cathode.

7. The electron gun according to claim 1, further comprising an energy source configured to supply energy to the cathode so that the cathode emits the electrons.

8. The electron gun according to claim 1, further comprising an electron receiving device configured to receive the backflow electrons passing through the through-hole of the cathode.

9. The electron gun according to claim 1, further comprising a focusing electrode for focusing the electrons emitted by the cathode into the electron beam.

10. The electron gun according to claim 1, characterized in that, The emission surface is concave, the grid includes a concave surface facing the anode, and the concave surface of the grid and the emission surface respectively correspond to two concentric circles.

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