Field emission X-ray tube of grid grouping regulation emitter

Abstract

The field emission X-ray tube comprises a vacuum maintaining assembly, a cathode assembly, an anode assembly and a window assembly, the cathode assembly comprises an emitter base, a regulation and control grid and a focusing electrode, the emitter base is provided with a plurality of electron emitters which are used for emitting electron beams and are arranged in an array, and the electron emitters are connected with the regulation and control grid. The regulation and control grid is arranged on one side of the emitter base in the emission direction of the electron beams, a plurality of electron beam through holes which are in one-to-one correspondence with the electron emitters and allow the electron beams to pass through are formed in the regulation and control grid, the electron beam through holes are divided into a plurality of regulation and control groups, and the electron beam through holes in the same regulation and control group are electrically connected; the electron beam through holes in different regulation and control groups are arranged in an insulated manner, and the plurality of regulation and control groups are independently regulated and controlled. According to the field emission X-ray tube, the plurality of electron emitters are regulated and controlled through the regulation and control grid, the regulation and control flexibility is improved, the total service life of the field emission X-ray tube is the sum of the service lives of all emission subsystems, the total service life is prolonged, and the cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of X-ray tubes, in particular to the technical field of field emission X-ray tubes used in the field of scientific instruments, and in particular to a field emission X-ray tube with a gate grouping regulating emitter. Background Art

[0002] X-ray tubes are playing an increasingly important role in many key fields such as aerospace, medical, new energy, additive manufacturing and electronic manufacturing. As a core component in the detection equipment, the quality of the X-ray tube is directly related to the performance of the entire detection equipment. In order to meet the diverse application needs, it is urgent to develop X-ray tubes with different functions.

[0003] As the core component of the X-ray tube, the performance of the electron source directly affects the efficiency and quality of X-ray generation. Existing X-ray tube electron sources are divided into thermal emission electron sources and field emission electron sources. Among them, thermal emission electron sources are widely used, but thermal emission electron sources still have some shortcomings. For example: 1. The thermal emission electron source needs to heat the cathode to a high temperature to achieve stable emission, which requires accurate temperature control to ensure the normal operation of the emitter, and this makes the electron gun start with a warm-up time; 2. The temperature control of the thermal emission electron source has hysteresis, which makes it difficult to respond quickly, resulting in the inability to quickly adjust the intensity of the X-ray. These shortcomings of the thermal emission electron source will limit its application; for example, in medical computed tomography (CT), the movement of organs is photographed, such as the pulsation of blood vessels and the beating of the heart. If the X-ray cannot be turned off quickly, and the turn-off frequency is lower than the movement frequency, motion artifacts will be generated, affecting the resolution of the image, and thus high-precision dynamic imaging cannot be achieved; and the imaging of thick fat tissue, bones or organs implanted under metal requires a larger tube current. If the tube current cannot be adjusted quickly according to the measurement situation, it will lead to photon starvation, image artifacts, and ultimately reduce the imaging accuracy.

[0004] Since the emission of field emission electron sources is mainly controlled by field effects, by controlling the gate through a specific voltage pulse signal, rapid electron shutoff can be achieved, thereby achieving a faster voltage and current response speed and preventing patients from being harmed by invalid rays. Although the field emission electron source has the above advantages, it still has some shortcomings: 1. The high field strength on the surface of the emitter will modify the emitter itself, causing the shape of the emitter to change with the electric field, resulting in a decrease in emission efficiency and even discharge damage; 2. The strong field strength on the surface of the emitter will cause ion back bombardment, thereby destroying the emitter and causing fluctuations in the emission current. This will seriously affect the life of the field emitter and increase the maintenance cost of the field emission X-ray source. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a field emission X-ray tube in which the emitter is controlled by grouping the gates. The working state of the emitter is controlled by grouping the gates and independently controlling each group, thereby increasing the control flexibility and extending the service life of the field emission X-ray tube.

[0006] To achieve the above object, the present invention provides a field emission X-ray tube with a grid grouping control emitter, comprising a vacuum maintenance component, a cathode component, an anode component, and a window component. The vacuum maintaining assembly includes a housing having a vacuum chamber therein; The cathode assembly comprises a cathode base sealed and fixed in a vacuum chamber, and an emitter base, a control grid and a focusing electrode all fixed to the cathode base. The emitter base is provided with a plurality of electron emitters arranged in an array for emitting electron beams. The control grid is provided on one side of the emitter base along the emission direction of the electron beam. The control grid is provided with a plurality of electron beam through holes corresponding to the electron emitters one by one and allowing the electron beam to pass through. The plurality of electron beam through holes are divided into an array of control groups. Each group of the control groups has at least one electron beam through hole. The electron beam through holes in the same group of the control groups are electrically connected, and the electron beam through holes in different groups of the control groups are insulated. The control groups in the array are independently controlled. The focusing electrode is used to focus the electron beams drawn out from the electron beam through holes. The anode assembly comprises an anode base which is sealed and fixed at one end of the shell and has a bombardment cavity therein, and an anode target installed in the bombardment cavity. The anode base is provided with an electron beam entrance hole and an X-ray outlet which are both connected to the bombardment cavity. The electron emitter is arranged opposite to the anode target via the electron beam through hole and the electron beam entrance hole in sequence. The window assembly is installed in the X-ray outlet.

[0007] Furthermore, the control grid is provided with conductive rows between the electron beam through holes in the same control group, the electron beam through holes in the same control group are electrically connected through the conductive rows of the control group, and the conductive rows of different control groups are insulated from each other.

[0008] Furthermore, the regulating grid includes an insulating substrate, the electron beam through hole penetrates the insulating substrate, and the conductive row is laid on the insulating substrate.

[0009] Furthermore, the control grid is a multi-layer structure, comprising an insulating layer, a conductive layer and a shielding layer stacked in sequence, the electron beam through hole penetrates the insulating layer, the conductive layer and the shielding layer, and the conductive layer constitutes a conductive row.

[0010] Furthermore, the control gate is a 3D printed part.

[0011] Furthermore, the field emission X-ray tube with the gate grouping regulating emitter also includes a vacuum feedthrough sealed and fixed at the other end of the shell, and a plurality of gate terminals, the vacuum feedthrough has a plurality of first terminals, and connecting electrodes are led out from the conductive row of each regulating group in the regulating gate, and the plurality of connecting electrodes are electrically connected to the plurality of first terminals of the vacuum feedthrough in a one-to-one correspondence through a plurality of gate terminals.

[0012] Furthermore, the electron beam through hole faces the center of the electron emitter along the emission direction of the electron beam.

[0013] Furthermore, the plurality of electron emitters and the plurality of electron beam through holes are arranged in a rectangular array; when a single group of the regulating groups has a plurality of electron beam through holes, the center distance between two adjacent electron beam through holes in the same group of the regulating groups is 0.15 to 0.25 mm.

[0014] Furthermore, the field emission X-ray tube for controlling the emitter by gate grouping also includes a vacuum feedthrough sealed and fixed at the other end of the shell, the vacuum feedthrough has a second terminal, the emitter base is made of metal or semiconductor and is provided with an emitter terminal, and the emitter terminal is electrically connected to the second terminal of the vacuum feedthrough.

[0015] Furthermore, the plurality of electron emitters arranged in an array are cut from a whole piece or several pieces of emission material fixed on a cathode base.

[0016] Furthermore, the plurality of electron emitters arranged in an array are formed by an emitting material coated on a cathode base.

[0017] Furthermore, the material of the electron emitter is carbon nanotube, graphene, or lanthanum hexaboride.

[0018] Furthermore, the focusing electrode comprises an independently controlled intermediate focusing electrode and a terminal focusing electrode, and the intermediate focusing electrode and the terminal focusing electrode are successively distributed along the emission direction of the electron beam.

[0019] Furthermore, the cathode assembly also includes a first insulating member, a second insulating member and a third insulating member, the first insulating member is separated between the emitter base and the control grid, the second insulating member is separated between the control grid and the intermediate focusing electrode, and the first insulating member is separated between the intermediate focusing electrode and the terminal focusing electrode.

[0020] Furthermore, the anode target is a rotating target rotatably mounted in the bombardment cavity, or is a fixed target fixed in the bombardment cavity.

[0021] Furthermore, the anode assembly also includes a target base and a cooling assembly, wherein the target base is fixed in the anode base and distributed on a side of the bombardment cavity away from the electron beam entrance hole, and the anode target is fixed on the end face of the target base facing the bombardment cavity; the cooling assembly includes a medium inlet passing through the anode base and the target base, a cooling cavity arranged in the target base, and a medium outlet passing through the anode base and the target base, and the medium inlet and the medium outlet are both connected to the cooling cavity; the material of the anode base is a high thermal conductivity material.

[0022] As described above, the field emission X-ray tube of the present invention in which the gate grouping and emitter is controlled has the following beneficial effects.

[0023] The present application divides the electron beam through holes on the control grid into control groups that are independently controlled in an array. By independently controlling the voltage at the electron beam through holes in each control group, the working state of the electron emitter corresponding to the electron beam through hole of the control group can be independently controlled, that is, the state of the electron beam emitted from the electron beam through hole of the control group can be independently controlled, thereby realizing the rapid switching of the electron focal spot size and beam size of the field emission X-ray tube. Therefore, the present application realizes the control of several electron emitters through the control grid, which increases the control flexibility on the one hand, and on the other hand, several electron emitters are equivalent to the emission subsystems corresponding to each control group divided into an array and the control grid, so that the total life of the field emission X-ray tube is the sum of the lifespans of all emission subsystems, thereby extending the total service life of the field emission X-ray tube, avoiding frequent replacement of the field emission X-ray tube, and effectively reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of the field emission X-ray tube of this application.

[0025] Figure 2 for Figure 1 sectional view of .

[0026] Figure 3 This is a schematic diagram of the structure of the cathode assembly in the field emission X-ray tube of the present application.

[0027] Figure 4 This is a schematic diagram of the structure of the anode assembly in the field emission X-ray tube of the present application.

[0028] Figure 5 This is a schematic diagram of the connection between the emitter base and the electron emitter in the cathode assembly of the present application.

[0029] Figure 6 This is a schematic diagram of the structure of the first embodiment of the control grid in the cathode assembly of the present application.

[0030] Figure 7a and Figure 7bThe electron trajectory diagram in two directions of the field emission X-ray tube equipped with the control grid embodiment 1 is shown.

[0031] Figure 8 The electron spot diagram emitted by different emission subsystems in the field emission X-ray tube equipped with the control grid embodiment 1 is shown.

[0032] Fig. 9 This is a schematic diagram of the structure of the second embodiment of the control grid in the cathode assembly of the present application.

[0033] Fig.10 The electron beam patterns emitted by different emission subsystems in the field emission X-ray tube equipped with the control grid embodiment 2 are shown.

[0034] Fig.11 This is a schematic diagram of the structure of the third embodiment of the control grid in the cathode assembly of the present application. DETAILED DESCRIPTION

[0035] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0036] It should be noted that the structures, proportions, sizes, etc. drawn in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0037] It should also be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element at the same time. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or may be indirectly connected to the other element through an intermediate element.

[0038] In addition, the descriptions of "first", "second", etc. in this application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0039] like Figure 1 and Figure 2 As shown, the present invention relates to the technical field of X-ray tubes, and in particular to a field emission X-ray tube in which a gate grouping and regulated emitter is used. Figure 2 In the view shown, the up-down direction of the paper is the axial direction of the field emission X-ray tube, that is, the length direction of the field emission X-ray tube. The field emission X-ray tube with grid grouping and emitter control involved in the present application includes a vacuum maintenance assembly 10, a cathode assembly 20, an anode assembly 30, and a window assembly 40.

[0040] like Figure 1 and Figure 2 As shown, the vacuum maintaining assembly 10 includes a housing 11, within which is a vacuum chamber 12 for forming a vacuum environment. The housing 11 is made of insulating material.

[0041] like Figure 2 and Figure 3 As shown, the cathode assembly 20 includes a cathode base 21, an emitter base 22, a control grid 23 and a focusing electrode 24. The cathode base 21 is sealed and fixed in the vacuum chamber 12 of the housing 11, and the emitter base 22, the control grid 23 and the focusing electrode 24 are all fixed in the cathode base 21; the emitter base 22 and the control grid 23 are arranged in sequence along the emission direction of the electron beam in the cathode assembly 20, and a plurality of electron emitters 25 arranged according to a specific rule are fixed on the end surface of the emitter base 22 facing the control grid 23, as shown in FIG. Figure 5 As shown, a plurality of electron emitters 25 are used to emit electron beams and are arranged in an array, and a control grid 23 is disposed on one side of the emitter base 22 along the emission direction of the electron beam; Figure 6 or Fig. 9 or Fig.11As shown, a plurality of electron beam through holes 231 are provided in the control grid 23, and a plurality of electron emitters 25 correspond to the plurality of electron beam through holes 231 one by one, or in other words, the plurality of electron emitters 25 and the plurality of electron beam through holes 231 are arranged one by one relative to each other along the emission direction of the electron beam, and the electron beam through holes 231 allow the electron beam emitted by the electron emitter 25 to pass through; in particular, the plurality of electron beam through holes 231 on the control grid 23 are divided into array control groups 232 according to actual application requirements, and each control group 232 has at least one electron beam through hole 231, the electron beam through holes 231 in the same control group 232 are electrically connected, and the electron beam through holes 231 in different control groups 232 are insulated from each other, and the array control groups 232 are independently controlled, that is, the voltage of the array control group 232 is independently controlled; the focusing electrode 24 is used to focus the electron beams drawn out from the electron beam through holes 231.

[0042] like Figure 2 and Figure 4 As shown, the anode assembly 30 includes an anode base 31 and an anode target 32. The anode base 31 is sealed and fixed at one end of the housing 11 along the emission direction of the electron beam in the cathode assembly 20. A bombardment cavity 311 is provided in the anode base 31. The anode target 32 ​​is installed in the bombardment cavity 311 at a set tilt angle. An electron beam incident hole 312 and an X-ray outlet 313 are provided in the anode base 31, both of which are connected to the bombardment cavity 311. The electron emitter 25 is arranged opposite to the anode target 32 ​​through the electron beam through hole 231 and the electron beam incident hole 312 in sequence. The window assembly 40 is installed in the X-ray outlet 313. In this embodiment, the hole axis of the electron beam incident hole 312 is perpendicular to the hole axis of the X-ray outlet 313. The electron beam incident hole 312 is an axial hole extending along the axial direction of the field emission X-ray tube, and the X-ray outlet 313 is a radial hole extending along the radial direction of the field emission X-ray tube.

[0043] During operation of the field emission X-ray tube with the above-mentioned gate grouping-controlled emitters, several electron emitters 25 emit electron beams, and the electron beam emitted by each electron emitter 25 passes through the electron beam through hole 231 corresponding to the electron emitter 25, and the state of the electron beam is controlled by the voltage at the electron beam through hole 231 that allows it to pass; then, the electron beam is accelerated by the electric field between the focusing electrode 24 and the anode base 31 to form a focused electron beam; the focused electron beam enters the bombardment cavity 311 of the anode base 31 through the electron beam entrance hole 312, thereby bombarding the anode target 32, thereby generating diffuse X-rays; the diffuse X-rays are emitted through the X-ray outlet 313, and the X-rays pass through the window assembly 40 and irradiate onto the desired workpiece.

[0044] In particular, the present application groups the electron beam through holes 231 on the control grid 23 according to the grouping requirements of the electron emitters 25, and divides a plurality of electron beam through holes 231 into a control group 232 for independently controlling power supply signals, thereby independently controlling the voltage at the electron beam through holes 231 in each control group 232, and independently controlling the working state of the electron emitter 25 corresponding to the electron beam through holes 231 of the control group 232, so as to achieve the purpose of independently controlling the state of the electron beam emitted from the electron beam through holes 231 of the control group 232, and realizing the rapid switching of the electron focal spot size and beam current size of the field emission X-ray tube. Therefore, the present application realizes grouped control of several electron emitters 25 by grouping control of several electron beam through holes 231 on the control grid 23. The several electron emitters 25 are equivalent to emission subsystems divided into arrays corresponding to each control group 232 of the control grid 23. On the one hand, the control flexibility is increased, and on the other hand, the total life of the field emission X-ray tube is the sum of the lifespans of all emission subsystems, thereby extending the total service life of the field emission X-ray tube, avoiding frequent replacement of the field emission X-ray tube, and effectively reducing costs.

[0045] The following describes the preferred structures of the components of the field emission X-ray tube.

[0046] Vacuum maintenance assembly 10

[0047] The shell 11 is a glass tube or a ceramic tube. One end of the shell 11 is connected to a cathode connection material by sintering to form a cathode connection part 13 fixed at one end of the shell 11, and the cathode connection part 13 is sealed and connected to the cathode base 21; the other end of the shell 11 is connected to an anode connection material by sintering to form an anode connection part 14 fixed at the other end of the shell 11, and the anode connection part 14 is sealed and connected to the anode base 31. In this way, the vacuum environment inside the shell 11 is ensured by the cathode connection part 13 and the anode connection part 14 at both ends of the shell 11.

[0048] Cathode assembly 20

[0049] Furthermore, the voltage regulation structure at the electron beam through hole 231 of each regulation group 232 in the regulation grid 23 is preferably as follows: Figure 6 or Fig. 9 or Fig.11As shown, the control grid 23 arranges conductive material on the corresponding electron beam through holes 231 according to the grouping requirements of the electron emitter 25, so that the control grid 23 is arranged with conductive rows 233 between the electron beam through holes 231 in the same control group 232; and the electron beam through holes 231 in the same control group 232 are electrically connected through the conductive rows 233 of the control group 232, so that the electrical connection and mutual conduction between the several electron beam through holes 231 in the same control group 232 are realized; and the conductive rows 233 of different control groups 232 are insulated from each other, so that the electron beam through holes 231 in different control groups 232 are insulated from each other and are non-conductive with each other.

[0050] Furthermore, there are many ways to arrange the conductive material on the control grid 23 .

[0051] Method 1: According to the grouping requirements of the electron emitters 25, the conductive material is laid on the electron beam through hole 231 of the insulating material; in this way, the control grid 23 includes an insulating substrate 234, the electron beam through hole 231 penetrates the insulating substrate 234, and the conductive bar 233 is laid on the insulating substrate 234. At this time, the laying method of the conductive material on the control grid 23 can be but is not limited to photolithography, electrodeposition, chemical etching, printing, evaporation and magnetron sputtering.

[0052] Method 2: The control grid 23 is formed by stacking multiple layers of materials; in this way, the control grid 23 is a multi-layer structure, and the control grid 23 includes an insulating layer, a conductive layer and a shielding layer stacked in sequence, the electron beam through hole 231 penetrates the insulating layer, the conductive layer and the shielding layer, the conductive layer constitutes a conductive row 233, there are multiple conductive layers, and they are insulated from each other, and the layers of the control grid 23 are fixed together by welding or hydraulic forming.

[0053] Method three: the control grid 23 is manufactured by 3D printing technology, and the control grid 23 is a 3D printed part.

[0054] Preferably, the hole constituting the electron beam through hole 231 on the control grid 23 is a small hole structure, and the shape of the electron beam through hole 231 can be circular, square, diamond, or other regular shapes. The processing method of the electron beam through hole 231 can be but is not limited to laser processing, electrochemical processing, micro-electrodischarge machining, ultrasonic processing, electronic processing and ion beam processing.

[0055] Furthermore, several electron beam through holes 231 on the control grid 23 are arranged one by one opposite to several electron emitters 25 along the emission direction of the electron beam, and the center of the electron beam through hole 231 is opposite to the center of the electron emitter 25. After such arrangement, firstly, the surface electric field of the electron emitter 25 is made as uniform as possible, the life of the electron emitter 25 is effectively extended, the shape of the electron emitter 25 is prevented from being modified by the electric field, and the emission stability and uniformity are reliably ensured; secondly, the electron beam through hole 231 is a small hole structure, so that the electron beam is led out through the small hole on the control grid 23, which can avoid the damage of the control grid 23 caused by the electron beam bombarding the control grid 23. Compared with the grid type grid, the present application significantly increases the electron transmittance; thirdly, under this position relationship, there is only a hole under the electron emitter 25, which can effectively block most of the return bombardment ions except the facing direction, avoid deformation and damage of the control grid 23, and damage of the electron emitter 25, and extend the service life of the control grid 23 and the electron emitter 25.

[0056] Furthermore, the array manufacturing method of several electron emitters 25 on the cathode base 21 is: cut along a set direction from a whole block or several blocks of emitting material fixed on the cathode base 21, and the cutting method of the emitting material can be but is not limited to laser processing and chemical etching; or, formed by an emitting material coated on the cathode base 21, and the coating method of the emitting material can be but is not limited to discharge method, ablation method and chemical vapor deposition method; or, several electron emitters 25 are directly fixed on the cathode base 21, and the fixing method can be but is not limited to welding, bonding and melting.

[0057] Preferably, the field emission array in the field emission X-ray tube may be a carbon nanotube array, a graphene array, or a lanthanum hexaboride array, and accordingly, the material of the electron emitter 25 is carbon nanotube, graphene, or lanthanum hexaboride.

[0058] Furthermore, if Figure 1 and Figure 2 As shown, the field emission X-ray tube with gate grouping regulating emitter also includes a vacuum feedthrough 50, which is sealed and fixed at one end of the shell 11 facing away from the anode base 31, and the electrical signal connection inside and outside the vacuum chamber 12 is realized through the vacuum feedthrough 50.

[0059] The electrical connection structure between the conductive bar 233 on the control grid 23 and the outside world is as follows: Figure 2 , Figure 3 and Figure 6As shown, the vacuum feedthrough 50 has several first terminals 51; a connection electrode 235 is led out from the conductive row 233 of each control group 232 in the control grid 23, and the connection electrodes 235 of each control group 232 are insulated from each other; several connection electrodes 235 are respectively connected to a gate terminal 26, and the other end of each gate terminal 26 is respectively connected to a first terminal 51 of the gate terminal 26, that is, several connection electrodes 235 of the control grid 23 are electrically connected to several first terminals 51 of the vacuum feedthrough 50 through several gate terminals 26, and several first terminals 51 are independently connected to the power supply. By adjusting each power supply signal separately, the pulse signal of the conductive row 233 of each control group 232 in the control grid 23 is independently regulated to realize the independent regulation of the voltage of each conductive row 233, thereby determining the working state of each emission subsystem corresponding to each control group 232. In addition, the gate terminal 26 is arranged in the emitter base 22, and the two are insulated.

[0060] The electrical connection structure between the electron emitter 25 and the outside world is as follows: Figure 2 and Figure 3 As shown, the vacuum feedthrough 50 has a second terminal 52, the emitter base 22 is made of metal or semiconductor and is provided with an emitter terminal 221, the emitter terminal 221 is separated from the gate terminal 26 and insulated from each other, and the emitter terminal 221 is electrically connected to the second terminal 52 of the vacuum feedthrough 50, so as to realize the electrical connection between the emitter base 22 and the outside world, thereby realizing the electrical connection between the plurality of electron emitters 25 at the bottom of the emitter base 22 and the outside world. By adjusting the power signal of the second terminal 52, the potential of the emitter base 22 and the electron emitter 25 can be changed.

[0061] Furthermore, the focusing electrode 24 may be a single electrode or a combination of multiple electrodes. Figure 2 and Figure 3 As shown, the focusing electrode 24 includes an independently controlled intermediate focusing electrode 241 and a terminal focusing electrode 242, which are successively distributed along the emission direction of the electron beam, and the focusing target is achieved by the intermediate focusing electrode 241 and the terminal focusing electrode 242. Among them, the intermediate focusing electrode 241 is cylindrical, and the terminal focusing electrode 242 includes an electrode barrel portion arranged on the outer peripheral side of the intermediate focusing electrode 241, and an electrode end plate portion arranged on one side of the intermediate focusing electrode 241 along the emission direction of the electron beam, and an axial through hole is opened in the electrode end plate portion.

[0062] Preferably, the intermediate focusing electrode 241 and the terminal focusing electrode 242 are independently wired to achieve independent voltage regulation of the intermediate focusing electrode 241 and the terminal focusing electrode 242 to better produce an X-ray focal spot that meets the working requirements. In this embodiment, the intermediate focusing electrode 241 is electrically connected to the outside through a vacuum feedthrough 50, and the terminal focusing electrode 242 is grounded.

[0063] Preferably, if Figure 2 and Figure 3 As shown, the cathode assembly 20 also includes a first insulating member 271, a second insulating member 272 and a third insulating member 273; the first insulating member 271 is separated between the emitter base 22 and the control grid 23, and at the same time accurately controls the axial distance between the emitter base 22 and the control grid 23, that is, accurately controls the axial distance between the electron emitter 25 and the control grid 23; the second insulating member 272 is separated between the control grid 23 and the intermediate focusing electrode 241; the first insulating member 271 is separated between the intermediate focusing electrode 241 and the terminal focusing electrode 242.

[0064] Furthermore, the plurality of electron emitters 25 and the plurality of electron beam through holes 231 are arranged in a rectangular array. There are many arrangements, and several preferred embodiments are provided below.

[0065] Embodiment 1

[0066] There are three rows of electron emitters 25 arrayed on the emitter base 22 with a diameter of 10 mm, each row has 19 circular electron emitters 25, and the size of each row of electron emitters 25 is 4 mm*0.5 mm; in each row of 19 electron emitters 25, the height of each electron emitter 25 in the axial direction of the field emission X-ray tube is 0.1 mm, and the center distance between two adjacent electron emitters 25 is 0.15-0.25 mm, preferably 0.2 mm. Correspondingly, there are also three rows of electron beam through holes 231 on the control grid 23, such as Figure 6 As shown, each row has 19 electron beam through holes 231, and each electron emitter 25 is axially opposite to each electron beam through hole 231; the electron beam through holes 231 are circular holes, and of course, they can also be holes of other regular shapes.

[0067] According to the grouping requirements of the electron emitter 25, such as Figure 6As shown, the several electron beam through holes 231 on the control grid 23 are divided into three control groups 232 by row, each control group 232 includes 19 electron beam through holes 231 arranged in a horizontal row, and the center distance between two adjacent electron beam through holes 231 in the same control group 232 is 0.15-0.25 mm, preferably 0.2 mm. The three control groups 232 are defined as control group 1 281, control group 282 and control group 3 283, respectively. Control group 1 281, control group 282 and control group 3 283 are all provided with conductive rows 233 electrically connected to the 19 electron beam through holes 231, and circular pads forming connecting electrodes 235 are led out at the ends of the conductive rows 233 to realize independent voltage control. In this way, the three-row electron emitter 25 has three emission subsystems. The conductive bars 233 of the first control group 281, the conductive bars 233 of the second control group 282 and the conductive bars 233 of the third control group 283 are insulated from each other. At the same time, an axially penetrating wiring through hole 236 is provided on the control grid 23 for electrical connection between the intermediate focusing electrode 241 and the vacuum feedthrough 50.

[0068] Taking the carbon nanotube array as an example, the surface field strength of the electron emitter 25 is about 6×10 6 V / m, using particle simulation software to simulate the trajectory of field emission electrons. By controlling the voltage of control group 1 281, control group 282 and control group 3 283, the emission subsystem corresponding to control group 3 283 is emitted, and the particle trajectory in the horizontal direction (defined as the Y direction) of the 19 electron beam through holes 231 in control group 3 283 is as follows: Figure 7a As shown, the particle trajectory in the direction perpendicular to the horizontal direction of the 19 electron beam through holes 231 in the three groups 283 (defined as the X direction) is as follows Figure 7b As shown, the particle trajectories show that focusing can be achieved in two directions.

[0069] At the same time, the light spot on the anode target 32 ​​is as follows: Figure 8 As shown, Figure 8 The left part is the light spot formed by regulating a group of 281 corresponding emission subsystems. Figure 8 The middle part is the light spot formed by regulating the emission subsystem corresponding to the two groups 282. Figure 8The right side of is the light spot formed by regulating the emission subsystems corresponding to the three groups 283. The simulation results show that when switching different emission subsystems, the emitted electrons can be focused on the target material with almost the same size, focusing on the Y length direction of about 1.8mm, focusing on the X direction of 0.05mm, and by coordinating with the angle of the anode target 32, the output of X-ray focal spots of different sizes can be achieved. The distance between the focal spots of different groups of electron emitters 25 in the X direction is 0.1mm. This method of adjusting the position of the focal point by adjusting the electric pulse of the gate 23 can realize the scanning of the focal position; the method of rotating the emission subsystem can effectively extend the life of the X-ray tube.

[0070] Embodiment 2

[0071] There is a row of 19 circular electron emitters 25 arrayed on the emitter base 22 with a diameter of 10 mm. The size of the electron emitters 25 in this row is 4 mm*0.5 mm. The height of each electron emitter 25 in the axial direction of the field emission X-ray tube is 0.1 mm. The center distance between two adjacent electron emitters 25 is 0.15-0.25 mm, preferably 0.2 mm. Correspondingly, there are also a row of 19 electron beam through holes 231 on the control grid 23, such as Fig. 9 As shown, each electron emitter 25 is axially opposite to each electron beam through hole 231, and the electron beam through hole 231 is a circular hole.

[0072] According to the grouping requirements of the electron emitter 25, such as Fig. 9 As shown, the 19 electron beam through holes 231 on the control grid 23 are divided into three groups of control groups 232 according to the row, and the three groups of control groups 232 are defined as control group 4 284, control group 5 285 and control group 6 286. Control group 4 284 includes 5 electron beam through holes 231 electrically connected in the middle, control group 5 285 includes 7 electron beam through holes 231 electrically connected on the left, and control group 6 286 includes 7 electron beam through holes 231 electrically connected on the right. The center distance between two adjacent electron beam through holes 231 in the same group of control groups 232 is 0.15-0.25 mm, preferably 0.2 mm. Control group 4 284, control group 5 285 and control group 6 286 lead out circular pads forming connection electrodes 235 at the end of each conductive row 233 to achieve independent voltage control. The conductive bars 233 of the fourth control group 284, the conductive bars 233 of the fifth control group 285 and the conductive bars 233 of the sixth control group 286 are insulated from each other. At the same time, an axially penetrating wiring through hole 236 is provided on the control grid 23 for electrical connection between the intermediate focusing electrode 241 and the vacuum feedthrough 50.

[0073] When the system needs to use a small focus, the required potential is given to the control group 4 284, and the control group 5 285 and the control group 6 286 are grounded or applied with a weak negative voltage to suppress the electron emission of the emission subsystem corresponding to the control group 5 285 and the control group 6 286, while avoiding the collision of stray electrons and causing charging. In this way, the electron beam is completely emitted by the five electron emitters 25 in the middle. Since the emission source size is small, the electron beam spot generated after the focusing electrode 24 is also small, which meets the system's demand for a small focus.

[0074] When the system needs to use a large focus and a large current, the required potentials are given to the control group 4 284, the control group 5 285 and the control group 6 286, respectively, and the emission subsystems corresponding to the control group 4 284, the control group 5 285 and the control group 6 286 all emit electron beams, so that the initial emission focal spot is enlarged and the emission beam current is increased. In this way, by quickly switching the electrical signals of the control group 4 284, the control group 5 285 and the control group 6 286, the electron beam current can be quickly increased or decreased.

[0075] Taking the carbon nanotube array as an example, the surface field strength of the electron emitter 25 is about 6×10 6 V / m, using particle simulation software to simulate the trajectory of field-emission electrons. The sizes of the two beam spots obtained by simulation are as follows Fig.10 As shown, the small focus spot size is about 1.4mm×0.1mm, the large focus spot size is 2mm×0.1mm, and the emission current increases from 5mA corresponding to the small focus to 20mA corresponding to the large focus.

[0076] Embodiment 3

[0077] There are nine circular electron emitters 25 arrayed on an emitter base 22 with a diameter of 10 mm. The nine electron emitters 25 are arrayed in three rows and three columns. Correspondingly, there are also nine electron beam through holes 231 on the control grid 23. Fig.11 As shown, nine electron beam through holes 231 are arranged in an array in three rows and three columns, each electron emitter 25 is axially opposite to each electron beam through hole 231, and the electron beam through holes 231 are square holes.

[0078] According to the grouping requirements of the electron emitter 25, such as Fig.11 As shown, the nine electron beam through holes 231 on the control grid 23 are divided into nine control groups 232 in rows, each control group 232 includes only one electron beam through hole 231, and the single electron beam through hole 231 in each control group 232 is led out through a conductive row 233, and a circular pad constituting a connecting electrode 235 is arranged at the end of each conductive row 233 to realize independent voltage control. At the same time, an axially penetrating wiring through hole 236 is provided on the control grid 23 for electrical connection between the intermediate focusing electrode 241 and the vacuum feedthrough 50.

[0079] The system increases or decreases the voltage of the control grid 23 according to the actual emission current, and introduces a feedback mechanism to stabilize the emission. More preferably, when the structure of a single electron emitter 25 is destroyed by the electric field and cannot produce effective emission, the remaining single electron emitters 25 can be switched to extend the life of the entire X-ray source.

[0080] The above three embodiments only show some examples of the grouping of the electron emitters 25 and the electron beam through holes 231. Other embodiments may adopt other grouping methods of the electron emitters 25 and the electron beam through holes 231 to achieve more precise control. The grouping methods of the electron emitters 25 and the electron beam through holes 231 in other embodiments include but are not limited to rectangle, ring, star, diamond, etc.

[0081] Anode assembly 30

[0082] The anode target 32 ​​is a rotating target rotatably mounted in the bombardment cavity 311, or a fixed target fixed in the bombardment cavity 311. The target material of the anode target 32 ​​includes but is not limited to tungsten target, copper target, molybdenum target, rhenium target, rhodium target, chromium target, gold target, silver target, platinum target, iron target and titanium target, and the target material of the anode target 32 ​​is selected according to the energy requirement of the X-ray. The anode target 32 ​​can be cooled by air, water or oil to ensure that the target material is not ablated, which effectively ensures the stability and service life of the field emission X-ray tube.

[0083] In this embodiment, the heat dissipation structure of the anode target 32 ​​is preferably: Figure 2 and Figure 4 As shown, the anode assembly 30 also includes a target base 33 and a cooling assembly; the target base 33 is fixed in the anode base 31 by welding or casting, and the target base 33 is distributed on the side of the bombardment cavity 311 away from the electron beam incident hole 312, and the anode target 32 ​​is fixed on the end face of the target base 33 facing the bombardment cavity 311; the cooling assembly includes a medium inlet 34 penetrating the anode base 31 and the target base 33, a cooling cavity 35 arranged in the target base 33, and a medium outlet 36 penetrating the anode base 31 and the target base 33, and the medium inlet 34 and the medium outlet 36 are both connected to the cooling cavity 35. Cooling medium such as cooling water or cooling oil flows into the cooling cavity 35 through the medium inlet 34, and then flows out through the medium outlet 36, and circulates in the cooling cavity 35, effectively dissipating heat for the target base 33 and the anode target 32, and improving the temperature stability of the anode target 32. At the same time, the material of the anode base 31 is a high thermal conductivity material, which effectively dissipates heat.

[0084] Window Components 40

[0085] The window assembly 40 is preferably made of beryllium or diamond to filter out low-energy electrons, reduce the heat dissipation pressure of the anode target 32, and reduce the amount of X-rays filtered. The window assembly 40 is fixed in the X-ray outlet 313 of the anode base 31 by welding or casting.

[0086] In summary, the field emission X-ray tube with the above-mentioned structure of gate grouping and regulated emitter has at least the following beneficial effects.

[0087] The field emission X-ray tube provided by the present invention realizes grouped control of a plurality of electron emitters 25 by grouping and controlling a plurality of electron beam through holes 231 on a control grid 23. The plurality of electron emitters 25 are equivalent to emission subsystems divided into arrays corresponding to the respective control groups 232 of the control grid 23. On the one hand, the control flexibility is increased, and on the other hand, the total life of the field emission X-ray tube is made the sum of the lifespans of all emission subsystems, thereby extending the total service life of the field emission X-ray tube.

[0088] In the field emission X-ray tube provided by the present invention, the surface electric field of the electron emitter 25 is relatively uniform, so that the electric field is prevented from modifying the shape of the electron emitter 25 and the life of the electron emitter 25 is prolonged.

[0089] In the field emission X-ray tube provided by the present invention, the electron beam through hole 231 on the control grid 23 is a small hole structure, which prevents the electron beam from bombarding the control grid 23 and effectively blocks most of the return ions except those in the facing direction, thereby extending the service life of the control grid 23 and the electron emitter 25.

[0090] The field emission X-ray tube provided by the present invention can better generate an X-ray focal spot that meets working requirements by independently adjusting the voltage of the intermediate focusing electrode 241 and the terminal focusing electrode 242.

[0091] In summary, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0092] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A field emission X-ray tube with a gate grouping control emitter, comprising a vacuum maintenance assembly (10), a cathode assembly (20), an anode assembly (30), and a window assembly (40), characterized in that: The vacuum maintaining assembly (10) comprises a housing (11) having a vacuum chamber (12) therein; The cathode assembly (20) comprises a cathode base (21) sealed and fixed in a vacuum chamber (12), an emitter base (22), a control grid (23) and a focusing electrode (24) all fixed to the cathode base (21); the emitter base (22) is provided with a plurality of electron emitters (25) arranged in an array and used for emitting electron beams; the control grid (23) is provided on one side of the emitter base (22) along the emission direction of the electron beam; the control grid (23) is provided with a plurality of holes corresponding to the electron emitters (25) and allowing the electron emitters (25) to be focused. An electron beam through hole (231) through which the electron beam passes, a plurality of the electron beam through holes (231) being divided into an array control group (232), each group of the control groups (232) having at least one electron beam through hole (231), the electron beam through holes (231) in the same group of the control groups (232) being electrically connected, the electron beam through holes (231) in different groups of the control groups (232) being insulated, the control groups (232) in the array being independently controlled, and the focusing electrode (24) being used to focus the electron beams drawn out from the electron beam through holes (231); The anode assembly (30) comprises an anode base (31) sealed and fixed at one end of the housing (11) and provided with a bombardment cavity (311), and an anode target (32) installed in the bombardment cavity (311); the anode base (31) is provided with an electron beam entrance hole (312) and an X-ray outlet (313) both of which are in communication with the bombardment cavity (311); the electron emitter (25) is arranged opposite to the anode target (32) via the electron beam through hole (231) and the electron beam entrance hole (312) in sequence; The window assembly (40) is installed in the X-ray outlet (313).

2. The field emission X-ray tube with gate grouping and emitter control according to claim 1, characterized in that: The control grid (23) is provided with conductive rows (233) between the electron beam through holes (231) in the same control group (232); the electron beam through holes (231) in the same control group (232) are electrically connected via the conductive rows (233) of the control group (232); and the conductive rows (233) of different control groups (232) are insulated from each other.

3. The field emission X-ray tube with gate grouping and emitter control according to claim 2, characterized in that: The control grid (23) comprises an insulating substrate (234), the electron beam through hole (231) penetrates the insulating substrate (234), and the conductive row (233) is laid on the insulating substrate (234).

4. The field emission X-ray tube with gate grouping and emitter control according to claim 2, characterized in that: The control grid (23) is a multi-layer structure, comprising an insulating layer, a conductive layer and a shielding layer stacked in sequence, the electron beam through hole (231) penetrates the insulating layer, the conductive layer and the shielding layer, and the conductive layer constitutes a conductive row (233).

5. The field emission X-ray tube with gate grouping and emitter control according to claim 2, characterized in that: The control grid (23) is a 3D printed part.

6. The field emission X-ray tube with gate grouping and emitter control according to claim 2, characterized in that: It also includes a vacuum feedthrough (50) sealed and fixed at the other end of the housing (11), and a plurality of gate terminals (26), the vacuum feedthrough (50) having a plurality of first terminals (51), a connection electrode (235) being led out from the conductive row (233) of each control group (232) in the control gate (23), and the plurality of connection electrodes (235) being electrically connected to the plurality of first terminals (51) of the vacuum feedthrough (50) in a one-to-one correspondence via a plurality of gate terminals (26).

7. The field emission X-ray tube with gate grouping and emitter control according to claim 1 or 2, characterized in that: The electron beam through hole (231) faces the center of the electron emitter (25) along the emission direction of the electron beam.

8. The field emission X-ray tube with gate grouping and emitter control according to claim 1, characterized in that: The plurality of electron emitters (25) and the plurality of electron beam through holes (231) are arranged in a rectangular array; when a single group of the regulating groups (232) has a plurality of electron beam through holes (231), the center distance between two adjacent electron beam through holes (231) in the same group of the regulating groups (232) is 0.15 to 0.25 mm.

9. The field emission X-ray tube with gate grouping and emitter control according to claim 1, characterized in that: It also comprises a vacuum feedthrough (50) sealed and fixed at the other end of the housing (11), the vacuum feedthrough (50) having a second connection terminal (52), the emitter base (22) being made of metal or semiconductor and being provided with an emitter connection terminal (221), the emitter connection terminal (221) being electrically connected to the second connection terminal (52) of the vacuum feedthrough (50).

10. The field emission X-ray tube with gate grouping and emitter control according to claim 1, characterized in that: The electron emitters (25) arranged in an array are cut from a whole piece or several pieces of emission material fixed on a cathode base (21).

11. The field emission X-ray tube with gate grouping and emitter control according to claim 1, characterized in that: The plurality of electron emitters (25) arranged in an array are formed by an emitting material coated on a cathode base (21).

12. The field emission X-ray tube with gate grouping and emitter control according to claim 1, characterized in that: The material of the electron emitter (25) is carbon nanotube, graphene, or lanthanum hexaboride.

13. The field emission X-ray tube with gate grouping and emitter control according to claim 1, characterized in that: The focusing electrode (24) comprises an independently controlled intermediate focusing electrode (241) and a terminal focusing electrode (242), wherein the intermediate focusing electrode (241) and the terminal focusing electrode (242) are successively distributed along the emission direction of the electron beam.

14. The field emission X-ray tube with gate grouping and emitter control according to claim 13, characterized in that: The cathode assembly (20) further comprises a first insulating member (271), a second insulating member (272) and a third insulating member (273), wherein the first insulating member (271) is separated between the emitter base (22) and the control grid (23), the second insulating member (272) is separated between the control grid (23) and the intermediate focusing electrode (241), and the first insulating member (271) is separated between the intermediate focusing electrode (241) and the terminal focusing electrode (242).

15. The field emission X-ray tube with gate grouping and emitter control according to claim 1, characterized in that: The anode target (32) is a rotating target rotatably mounted in the bombardment inner cavity (311), or is a fixed target fixed in the bombardment inner cavity (311).

16. The field emission X-ray tube with gate grouping and emitter control according to claim 1, characterized in that: The anode assembly (30) further comprises a target base (33) and a cooling assembly. The target base (33) is fixedly arranged in the anode base (31) and distributed on a side of the bombardment cavity (311) away from the electron beam entrance hole (312). The anode target (32) is fixed on an end surface of the target base (33) facing the bombardment cavity (311). The cooling assembly comprises a medium inlet (34) penetrating the anode base (31) and the target base (33), a cooling cavity (35) arranged in the target base (33), and a medium outlet (36) penetrating the anode base (31) and the target base (33). Both the medium inlet (34) and the medium outlet (36) are in communication with the cooling cavity (35). The material of the anode base (31) is a high thermal conductivity material.

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