Electron Gun

Abstract

An electron gun may include a cathode, wherein the cathode emission surface is configured to emit electrons. The cathode may include a through hole passing through the emission surface, wherein the through hole is configured to allow return electrons of the 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. The electron gun may also include a grid structure configured to facilitate focusing of the electrons into the electron beam, wherein the position of the grid structure corresponds to the through hole.

Description

Technical Field

[0001] The present application relates to an electron gun, and more particularly to an electron gun comprising a hollow cathode and a mesh structure, wherein the mesh structure is configured to reduce or eliminate backflow electrons on the cathode. Background Art

[0002] 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

[0003] According to one aspect of the present specification, an electron gun may include a cathode having an emission surface, the emission surface being configured to emit electrons, the cathode including a through hole passing through the emission surface, the through hole being configured to allow return 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.

[0004] In some embodiments, at least one of the cathode, the through-hole, the grid structure, or the anode is centered about a common axis of the electron gun.

[0005] In some embodiments, a projection of at least a portion of the grid structure along the common axis is located within a cross section of the through hole, and the cross section is perpendicular to the common axis.

[0006] In some embodiments, the voltage of the grid structure is the same as the voltage of the cathode.

[0007] In some embodiments, the grid structure includes two or more first meshes, and the returning electrons pass through the two or more first meshes.

[0008] In some embodiments, the two or more first meshes are related to counting the returning electrons passing through the mesh structure and focusing the electrons emitted from the cathode.

[0009] In some embodiments, the grid structure is in contact with the cathode.

[0010] In some embodiments, there is a gap between the mesh structure and the cathode.

[0011] In some embodiments, the lattice structure is supported by a lattice support.

[0012] In some embodiments, the cathode includes a first material configured to facilitate emission of the electrons from the cathode by reducing a work function of the cathode.

[0013] In some embodiments, the mesh structure includes a second material that chemically reacts with the first material.

[0014] In some embodiments, the first material includes barium (Ba), and the second material includes a transition metal including at least one of zirconium (Zr) or hafnium (Hf).

[0015] In some embodiments, the second material is configured to prevent the mesh structure from emitting electrons due to impact of at least a portion of the returning electrons on the mesh structure.

[0016] In some embodiments, the electron gun further includes a grid configured to control the flow of the electrons emitted from the cathode to the anode, the grid being located between the cathode and the anode.

[0017] In some embodiments, the grid has the common axis of the electron gun as its central axis.

[0018] In some embodiments, the gate includes two or more second meshes configured to allow the electrons emitted from the cathode or the return electrons to pass therethrough.

[0019] In some embodiments, the two or more second meshes include a central mesh corresponding to the through hole, the central mesh is configured to allow the return electrons to pass through and prevent the return electrons from impacting the gate, and the central mesh has the common axis as a central axis.

[0020] In some embodiments, the gate includes a third material that chemically reacts with the first material.

[0021] In some embodiments, the mesh structure is located in a fixed position between the cathode and the gate.

[0022] In some embodiments, the position of the grid structure is adjustable along the common axis between the cathode and the gate.

[0023] In some embodiments, the electron gun further includes an energy source configured to provide energy to the cathode, thereby causing the cathode to emit the electrons.

[0024] In some embodiments, the electron gun further includes an electron receiving device configured to receive the return electrons passing through the through-holes of the cathode.

[0025] In some embodiments, the electron gun further includes a focusing electrode for focusing the electrons emitted from the cathode into the electron beam.

[0026] Some additional features of the present application may be explained in the following description. Some additional features of the present application will be apparent to those of ordinary skill in the art through study of the following description and corresponding drawings or understanding of the production or operation of the embodiments. The features of the present application may be realized and achieved through practice or use of the methods, means and combinations of various aspects of the specific embodiments described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] This specification will be further described in the form of exemplary embodiments. These exemplary embodiments will be described in detail by way of the accompanying drawings. These embodiments are non-limiting exemplary embodiments, in which the same numbers in each figure represent the same structure, wherein:

[0028] Figure 1 and Figure 2 is a schematic diagram of a cross section of an exemplary triode electron gun according to some embodiments of the present specification;

[0029] Figure 3 is a schematic diagram of an exemplary grid structure according to some embodiments of the present specification. DETAILED DESCRIPTION

[0030] 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, it should be understood by those skilled in the art 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 the general principles defined in this specification can be applied to other embodiments and application scenarios without departing from the principles and scope of this specification. Therefore, this specification is not limited to the embodiments shown, but conforms to the broadest scope consistent with the patent scope of the specification.

[0031] The terms used in this specification are only for describing specific exemplary embodiments and do not limit the scope of this specification. As shown in this specification and claims, unless the context clearly indicates an exception, the words "one", "a", "a kind" and / or "the" do not specifically refer to the singular and may also include the plural. It should be understood that the terms "including" and "comprising" used in this specification only indicate the features, wholes, steps, operations, elements, and / or components that have been clearly identified, and do not exclude the existence and addition of one or more other features, wholes, steps, operations, elements, components, and / or any combination thereof.

[0032] It should be noted that the terms "system", "device", "unit" and / or "module" used in this specification are a method for distinguishing different components, elements, parts, parts or assemblies at different levels. However, if other expressions can achieve the same purpose, the terms can be replaced by other expressions.

[0033] Generally, the words "system", "device", "unit" and / or "module" used in this specification refer to 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 system, device, unit and / or module may be compiled and linked into an executable program. It should be understood that software modules may be called from other systems, devices, units, modules and / or from themselves, and / or may be called in response to detected events or interrupts. Software systems, devices, units and / or modules configured for execution on a computing device may be provided on a computer-readable medium, such as an optical disc, a digital video disc, a flash drive, a disk or any other tangible medium, or as a digital download (and may be initially stored in a compressed or installable format, requiring installation, decompression or decryption prior to execution). The software code here may be stored in part or in whole in a storage device of a computing device performing the operation, and applied in the operation of the computing device. Software instructions may be embedded in firmware, such as an EPROM. Further, hardware modules / units / blocks may include connected logical components, such as gates, triggers, and / or programmable units, such as programmable gate arrays or processors. The systems, devices, 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, devices, units, and / or modules described herein refer to logical systems, devices, units, and / or modules, which may be combined with other systems, devices, units, and / or modules or divided into subsystems, subdevices, subunits, and / or submodules, regardless of their physical organization or storage devices.

[0034] It should be understood that when a system, device, unit and / or module refers to being "located in," "connected to," or "coupled to" another system, device, unit and / or module, unless the context clearly indicates otherwise, these systems, devices, units and / or modules may be directly located in, connected to, coupled to other systems, devices, units and / or modules, or there may be intermediate systems, devices, units and / or modules. In this specification, the term "and / or" may include any one or a combination of at least one of the related listed items.

[0035] The features, characteristics, methods of operation, functions of related structural elements, combinations of parts, and economies of manufacture described in this specification and others will become more apparent after considering the descriptions of the drawings which form a part of this specification. However, it should be understood that the drawings are for illustration and description purposes only and are not intended to limit the scope of this specification. It should be understood that the drawings are not drawn to scale.

[0036] Linear particle accelerators, or klystrons, use an electron beam source, commonly referred to as an electron gun. For example, in some cases, when an electron gun is used as an electron source in an electron linear accelerator, a portion of the electrons output from the electron gun (referred to as backflow electrons) may return to the electron gun. The backflow electrons may adversely affect 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 that mitigates or addresses the effects of the backflow electrons on the cathode.

[0037] One aspect of the present 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 passage of backflow electrons. The backflow electrons may pass through the through hole instead of hitting the cathode, thereby avoiding overheating of the cathode. The electron gun may also include a grid structure configured to facilitate the focusing of 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. The projection of at least a portion of the grid structure along the common axis may be located within a cross section of the through hole, and the cross section is perpendicular to the common axis. Due to the presence of the through hole, the emission surface of the cathode may be discontinuous, and the electric field formed between the cathode and the anode based on the discontinuity may focus the electrons emitted from the cathode into an electron beam, but the convergence of the electron beam is relatively poor. Using the grid structure, the electric field between the cathode and the anode may focus the electrons emitted from the cathode into an electron beam, and the electron beam has better convergence than without the grid structure.

[0038] Figure 1 and Figure 21 is a schematic diagram of a cross section of an exemplary triode electron gun according to some embodiments of the present specification. The electron gun 100 may include a cathode 110, a grid structure (e.g., Figure 1 The grid structure in 121 or Figure 2 In some embodiments, the cathode 110, the gate 130, and the anode 140 may be centered on a common axis 160 of the electron gun 100. In some embodiments, the electron gun 100 may further include 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, the anode 140 may be located downstream of the cathode 110 along the emission direction of the electrons emitted from the cathode 110. The gate 130 may be located between the cathode 110 and the anode 140. The focusing electrode 150 may be located between the gate 130 and the anode 140.

[0039] In some embodiments, Figure 1 The X-axis, Y-axis, and Z-axis shown in the figure may form an orthogonal coordinate system. As shown in the figure, 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. Figure 1 In the figure, for convenience of explanation, the X-axis may be represented as being 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 are similar to Figure 1 The X-axis, Y-axis and Z-axis in the Figure 1 and Figure 2 A cross section of the electron gun 100 parallel to the YZ plane is shown.

[0040] Cathode 110 may include an emitting surface 112 configured to emit electrons. In some embodiments, emitting surface 112 may face anode 140. Emitting surface 112 may be a flat surface or a curved surface (e.g., Figure 1 In some embodiments, the emitting surface 112 may be centered about the common axis 160.

[0041] When the temperature of the metal increases, the kinetic energy of the electrons in the metal may increase accordingly. When the temperature increases 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 thermal electron emission. In some embodiments, the cathode 110 may be so hot that electrons are emitted from the emission surface 112 by thermal electron emission.

[0042] In some embodiments, the cathode 110 (e.g., the emission surface 112) may include a metal material, such as tungsten (W) and its alloys. By heating the cathode 110, the outer electrons of the atoms of the metal material may be excited by a specific energy. The excited electrons may overcome the work function of the metal material and escape from the constraints of the orbit to become free electrons emitted from the cathode 110 (e.g., the emission surface 112). The energy required for 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 also include a first material, such as barium (Ba), which is configured to promote 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 a first material.

[0043] Electrons emitted from the cathode 110 (also referred to as emitted electrons) may fly out of the electron gun 100 by attraction of the anode 140. In some cases, a portion of the emitted electrons (called reflux electrons) may return to the electron gun 100. For example, when the electron gun 100 is used as an electron source for an electron linear accelerator, the electron linear accelerator may be connected to the anode 140. The emitted electrons may enter the electron linear accelerator from the electron gun 100 through the anode 140. Since the frequency at which the emitted electrons are injected into the electron linear accelerator from the electron gun 100 is not synchronized with the frequency of the accelerating field (e.g., an electric field or an electromagnetic field) used to accelerate the emitted electrons and applied to the electron linear accelerator, some emitted electrons are accelerated in a direction opposite to the emission direction of the electrons emitted by the cathode 110, thereby returning to the electron gun 100. It should be noted that the electron gun provided in the present disclosure may also be used to reduce or eliminate reflux electrons caused by other reasons.

[0044] Assuming that the cathode 110 is solid, the return electrons will hit the cathode 110, for example, in the area of ​​the emission surface 112 centered on the common axis 160. The return electrons that hit the cathode 110 may cause the temperature of the cathode 110 to increase, thereby causing the cathode 110 to overheat. 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 increasing temperature. Therefore, overheating of the cathode 110 may accelerate the evaporation rate of the first material, thereby reducing the life of the cathode 110. For another example, the evaporated first material may be deposited 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 electric field gradient inside the electron linear accelerator, the electrons emitted from the inner wall of the electron linear accelerator may form a "dark current" and consume the power of the electron linear accelerator.

[0045] In some embodiments of the present invention, Figure 1As shown, the cathode 110 may be a hollow cathode including a first through hole 114 passing through the emission surface 112 and configured to allow the return electrons of the emitted electrons to pass through. The first through hole 114 may extend along the common axis 160 and pass through the cathode 110. The return electrons may pass through the first through hole 114 instead of striking the cathode 110, thereby preventing the return electrons from overheating the cathode 110.

[0046] 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 emitted electrons flow back through the first through hole 114 instead of hitting the cathode 110. For example, the first through hole 114 can have the common axis 160 as the central axis. For another example, the first through hole 114 can be a cylinder whose cross section is a circle parallel to the XY plane.

[0047] Due to the different voltages on the components in the electron gun 100 (e.g., the cathode 110, the grid 130, the focusing electrode 150, the anode 140, etc.), an electric field including curved equipotential surfaces and / or electric field lines may be formed between the cathode 110 and the anode 140, which may 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 may leave the electron gun 100 in the form of an electron beam.

[0048] The electric field between cathode 110 and anode 140 formed by discontinuous emission surface 112 having holes corresponding to first through holes 114 can focus the emitted electrons into an electron beam, but the convergence of the electron beam is relatively poor. To improve the focusing of the emitted electrons, a grid structure can be applied in electron gun 100.

[0049] The grid structure can be configured to facilitate focusing of emitted electrons. In some embodiments, the grid structure can be located between the cathode 110 and the anode 140. In some embodiments, the location 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, the projection of at least a portion of the grid structure along the negative direction of the Z axis can be located within a cross section of the first through hole 114 parallel to the XY plane. For example, the projection of the entire grid structure along the negative direction of the Z axis can be located within a cross section of the first through hole 114 parallel to the XY plane. For another example, the projection of the first portion of the grid structure along the negative direction of the Z axis can be located within a cross section of the first through hole 114 parallel to the XY plane, while the projection of the second portion of the grid structure along the negative direction of the Z axis can be located outside the cross section of the first through hole 114 parallel to the XY plane.

[0050] 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 with better convergence than without the grid structure.

[0051] In some embodiments, the grid structure may include a first grid frame and two or more first meshes through which the return electrons of the emitted electrons may pass. The first grid frame may include a plurality of crossing wires (e.g., electrical wires). The first grid frame may define the two or more first meshes.

[0052] Just as an example, Figure 3 is a schematic diagram of an exemplary grid structure according to some embodiments of the present specification. Figure 3 Shown in Figure 1 or Figure 2 3 is a view of the grid structure 300 seen from the positive or negative direction of the Z axis. As shown in the figure, the grid structure 300 may include a first grid frame 310 and two or more first meshes (e.g., mesh 320), through which the returning electrons may pass. The first grid frame may include a plurality of crossing wires (e.g., electric wires).

[0053] In some embodiments, the grid pattern of the grid structure determined based on the first grid frame and the two or more first meshes may indicate the size, shape, number of the two or more first meshes, total area of ​​the two or more first meshes, thickness of the cross lines forming the first grid frame, density of the two or more first meshes in the grid structure (e.g., number of first meshes 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 meshes, the more return electrons may pass through the grid structure, but the focusing performance of the grid structure may be worse. The grid pattern of the grid structure may be configured so that most (e.g., at least 60%, at least 70%, at least 80%, at least 90%, etc.) of the return 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.

[0054] In some embodiments, the mesh 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, in order to prevent thermal electron emission of the mesh structure, the mesh structure may be thermally isolated from the cathode 110, and / or the work function of the mesh structure may be higher than that of the cathode 110.

[0055] 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 that impact 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 embodiment 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, the transition metal including 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 impact of at least a portion of the backflow electrons on the grid structure.

[0056] In some embodiments, the grid structure (e.g., Figure 1 The mesh structure 121 shown in FIG. 1 may be in contact with the cathode 110. For example, the mesh structure may be welded to the cathode 110. In some embodiments, there may be a gap between the mesh structure and the cathode 110. For example, as shown in FIG. Figure 2 As shown, there may be a gap 170 between the grid structure 122 and the cathode 110. In some embodiments, the grid structure may be supported by a grid support. Figure 2 As 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 thermal electron 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 emission of electrons from the grid support 180 due to at least a portion of the backflow electrons hitting the grid support 180, the grid support 180 can include a material that chemically reacts with the first material. The material can be similar to the second material of the grid structure described elsewhere in this specification, and will not be repeated here.

[0057] In some embodiments, the mesh structure can be located between the cathode 110 and the anode 140. In some embodiments, the mesh structure can be closer to the cathode 110 relative to the anode 140. In some embodiments, the mesh structure can be located at a fixed position between the cathode 110 and the anode 140. In some embodiments, the position of the mesh structure can be adjustable, for example, between the cathode 110 and the anode 140 along the common axis 160.

[0058] In some embodiments, the grid structure can be located between the cathode 110 and the grid electrode 130. In some embodiments, the grid structure can be located at a fixed position between the cathode 110 and the grid electrode 130. In some embodiments, the position of the grid structure can be adjustable, for example, along the common axis 160 between the cathode 110 and the grid electrode 130.

[0059] The gate 130 may be configured to control the flow of emitted electrons from the cathode 110 to the anode 140. For example, if the gate 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 deceleration electric field for emitted electrons. The emitted electrons may escape from the cathode 110 at an initial velocity. Due to the deceleration electric field between the gate 130 and the cathode 110, electrons with a relatively small initial velocity may return to the cathode 110, and 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 may be controlled by adjusting the voltage of the gate 130. When the gate 130 maintains a sufficiently high negative voltage relative to the cathode 110, all emitted electrons may be driven back to the cathode 110, so that no electrons move to the anode 140. If the voltage of the gate 130 is positive relative to the cathode 110, an accelerating electric field for emitted electrons is formed between the gate 130 and the cathode 110, and the emitted electrons move toward the anode 140.

[0060] In some embodiments, the gate 130 may provide the same voltage as the focusing electrode 150. In some embodiments, if the emission surface 112 is a concave surface, the gate 130 may include a concave surface facing the anode 140. The concave surface of the gate 130 and the emission surface 112 may correspond to two concentric circles, respectively.

[0061] In some embodiments, the grid 130 may include a second grid frame and two or more second meshes, the two or more second meshes being configured to allow electrons emitted from the cathode and moving to the anode 140 to pass through, and / or allow return electrons to pass through and reach the cathode 110. The second grid frame may include a plurality of crossing wires (e.g., electrical wires). The two or more second meshes may be defined by the second grid frame.

[0062] In some embodiments, the grid pattern of the gate 130 determined based on the second grid frame and the two or more second meshes may indicate the size, shape of each of the two or more second meshes, the number of two or more second meshes, the total area of ​​the two or more second meshes, the thickness of the intersection lines forming the second grid frame, the density of the two or more second meshes in the gate 130 (for example, the number of second meshes per unit area in the gate 130), etc., or any combination thereof.

[0063] In some embodiments, a portion 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 portion of the gate 130 corresponding to the grid structure may refer to an area on the gate 130 that is covered by the projection of the grid structure on the gate 130 along the positive direction of the Z axis.

[0064] 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 backflow electrons that strike the second grid frame of the gate 130 may cause the temperature of the gate 130 to increase, causing the gate 130 to emit electrons. When the gate 130 is configured to reduce or eliminate the number of electrons that move to the anode 140, it means that a small number 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 backflow electrons that strike 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.

[0065] The first through hole 114 can alleviate or solve the above-mentioned problem of the gate 130 by avoiding or reducing overheating of the cathode 110 caused by the impact of the backflow electrons on the cathode 110 .

[0066] In some embodiments, in order to further alleviate or solve the above-mentioned problems of the gate 130, the two or more second meshes of the gate 130 may include a central mesh 132 corresponding to the first through hole 114, and the central mesh 132 is configured to allow the return electrons to pass through and prevent the return electrons from hitting the gate 130. In some embodiments, the central mesh 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 the common axis 160. The shape of the central mesh 132 may be the same or similar to the cross-sectional shape of the first through hole 114 parallel to the XY plane, and the size of the central mesh 132 may be equal to, greater than, or less 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 including at least one of zirconium (Zr) or hafnium (Hf) that chemically reacts with Ba. The third material may be configured to reduce or prevent deposition of the first material on the gate 130 and / or emission of electrons from the gate 130 due to at least a portion of the returning electrons impacting the electrode 130 .

[0067] In some embodiments, when the projection of the entire grid structure along the Z-axis direction extends beyond the first through hole 114 , the grid structure can intercept the return electrons that would otherwise be intercepted by the gate 130 , thereby reducing the pressure on the gate 130 to intercept the return electrons.

[0068] 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.

[0069] The focusing electrode 150 may be configured to focus the emitted electrons into an electron beam.

[0070] The energy source may be configured to provide energy (eg, thermal energy or electrical energy) to the cathode 110 , such that electrons can be emitted from the cathode 110 (eg, thermionic emission).

[0071] The electron receiving device may be configured to receive the return electrons of the emitted electrons through the first through hole 114 of the cathode 110. In some embodiments, the electron receiving device may include a metal material electrically connected to the ground. In some embodiments, the electron receiving device may be located upstream of the cathode 110 along the positive direction of the Z axis.

[0072] In some embodiments, the cathode 110 having the first through hole 114 and the grid structure shown in this specification can also be applied to a diode electron gun to alleviate or solve the cathode overheating caused by the backflow electrons impacting the cathode.

[0073] 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 according to the description of this specification. However, these changes and modifications do not depart from the scope of this specification.

[0074] The basic concepts have been described above. Obviously, for those of ordinary skill in the art who have read this application, the above disclosure is only for example and does not constitute a limitation of this application. Although not explicitly stated here, those of ordinary skill in the art may make various modifications, improvements and amendments to this application. Such modifications, improvements and amendments are suggested in this application, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of this application.

[0075] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment", "an embodiment", and / or "some embodiments" mentioned twice or more in different positions in the present application do not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0076] In addition, it will be appreciated by those skilled in the art that the various aspects of the present application may be illustrated and described by a number of patentable categories or situations, including any new and useful combination of processes, machines, products or substances, or any new and useful improvements thereto. Accordingly, the various aspects of the present application may be performed 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 may all be referred to as "data blocks", "modules", "engines", "units", "components" or "systems". In addition, the various aspects of the present application may take the form of a computer program product embodied in one or more computer-readable media, wherein computer-readable program codes are contained therein.

[0077] In addition, unless explicitly stated in the claims, the order of the processing elements and sequences described in this application, the use of alphanumeric characters, or the use of other names are not intended to limit the order of the processes and methods of this application. Although the above disclosure discusses some invention embodiments that are currently considered useful through various examples, it should be understood that such details are only for illustrative purposes, and the attached claims are not limited to the disclosed embodiments. On the contrary, the claims are intended to cover all modifications and equivalent combinations that are consistent with 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 by software solutions, such as installing the described system on an existing server or mobile device.

[0078] Similarly, it should be noted that in order to simplify the description of the disclosure of this application and thus help understand one or more embodiments of the invention, in the above description of the embodiments of the present application, multiple features are sometimes combined into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the object of the present application are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

Claims

1. An electron gun, characterized in that: include: a cathode having an emission surface, the emission surface being configured to emit electrons, the cathode comprising a through hole passing through the emission surface, the through hole being configured to allow return electrons of the electrons emitted by the emission surface to pass therethrough; an anode configured to attract the electrons emitted from the emission surface from the cathode to the anode and focus the electrons into an electron beam; a grid structure configured to facilitate focusing of the electrons into the electron beam, the grid structure being located corresponding to the through-holes; and The cathode includes a first material configured to facilitate emission of the electrons from the cathode by reducing a work function of the cathode.

2. The electron gun according to claim 1, characterized in that At least one of the cathode, the through hole, the grid structure or the anode has a common axis of the electron gun as a central axis.

3. The electron gun according to claim 2, characterized in that A projection of at least a portion of the grid structure along the common axis is located within a cross section of the through hole, and the cross section is perpendicular to the common axis.

4. The electron gun according to claim 2, characterized in that The voltage of the grid structure is the same as the voltage of the cathode.

5. The electron gun according to any one of claims 2 to 4, characterized in that: The grid structure includes two or more first meshes, and the returning electrons pass through the two or more first meshes. 6 . The electron gun according to claim 5 , wherein the two or more first meshes are related to counting of the return electrons passing through the grid structure and focusing of the electrons emitted from the cathode. The electron gun according to claim 2 , wherein the grid structure is in contact with the cathode. The electron gun according to claim 2 , wherein a gap exists between the grid structure and the cathode.

9. The electron gun according to claim 2, wherein the grid structure is supported by a grid support.

10. The electron gun of claim 1, the grid structure comprising a second material that chemically reacts with the first material. 11 . The electron gun according to claim 10 , wherein the first material comprises barium (Ba), and the second material comprises a transition metal, and the transition metal comprises at least one of zirconium (Zr) or hafnium (Hf).

12. The electron gun of claim 10, wherein the second material is configured to prevent the mesh structure from emitting electrons due to impact of at least a portion of the returning electrons on the mesh structure.

13. The electron gun according to claim 1, further comprising a grid configured to control the flow of the electrons emitted from the cathode to the anode, the grid being located between the cathode and the anode.

14. The electron gun according to claim 13, wherein the grid has the common axis of the electron gun as a center axis. 15 . The electron gun according to claim 13 , wherein the grid comprises two or more second meshes configured to allow the electrons emitted from the cathode or the return electrons to pass therethrough.

16. The electron gun according to claim 15, wherein the two or more second meshes include a central mesh corresponding to the through hole, the central mesh being configured to allow the return electrons to pass through and prevent the return electrons from impacting the grid, and the central mesh having the common axis as a central axis.

17. The electron gun of claim 13, wherein the grid electrode comprises a third material that chemically reacts with the first material.

18. The electron gun according to claim 13, wherein The grid structure is located at a fixed position between the cathode and the grid.

19. The electron gun of claim 13, wherein the position of the grid structure is adjustable along the common axis between the cathode and the grid.

20. The electron gun of claim 1, further comprising an energy source configured to provide energy to the cathode so as to cause the cathode to emit the electrons.

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

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

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