Field emission X-ray tube with movable 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 a cathode base, a mobile regulation and control assembly, an emitting electrode, a grid electrode and a focusing electrode, and the emitting electrode comprises an emitter supporting column and an electron emitter which are fixed to each other. The cathode base is provided with a shielding base surface and a supporting hole, the emitter supporting column is movably contained in the supporting hole, and the part, located between the shielding base surface and the emitter supporting column, of the supporting hole forms an emitter storage cavity. The electron emitter is provided with an emitter storage section contained in the emitter storage cavity and an emitter working section protruding out of the surface of the shielding base, and the movable regulation and control assembly drives the emitter supporting column and the electron emitter to move in the direction close to or away from the grid electrode. The field emission X-ray tube has a storage function for the emitter, regeneration of the working section of the emitter is achieved, the service life of the field emission X-ray tube is prolonged, and the tube bundle flow regulation and control flexibility of the X-ray tube is improved.

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 movable emitter. Background Art

[0002] X-ray tubes are essential components in medical imaging, materials science, and industrial testing. They generate high-energy X-rays for perspective and analysis, and are crucial for diagnosing diseases, studying material microstructures, and detecting product defects. Field emission X-ray tubes are becoming a new technology to replace traditional hot cathode X-ray tubes with their significant advantages such as high spatial resolution, low power consumption, easy integration, and fast emission response. They are particularly suitable for applications that require fine imaging, rapid diagnosis, and low-dose radiation, such as medical imaging, industrial testing, and safety inspections.

[0003] However, field emission X-ray tubes also have some significant disadvantages: since the emitter surface of the field emission X-ray tube requires a strong electric field to enable electron tunneling emission; however, under a strong field, the emitter structure will be further destroyed. At present, there are mainly the following mechanisms for the destruction of the emitter structure.

[0004] 1. When the distance between the emitter and the gate is not properly controlled, the high field strength on the emitter surface causes discharge, resulting in damage to the emitter.

[0005] 2. Under high emission current conditions, the temperature at the electron emission point of the emitter will rise rapidly, resulting in the "Ohmic heating" phenomenon. Thermal emission gradually begins to dominate, causing the emitter structure to be destroyed, affecting the final emission effect.

[0006] 3. Under the condition of high electric field on the surface, the emitter emits high-energy electrons to bombard gas molecules, target materials, and the inner wall of the electrode in the vacuum tube to produce positive ions. Due to the high field strength on the surface of the emitter, these ions will be accelerated back to the emitter, resulting in a decrease in the emission capability of the emitter.

[0007] The emitter destruction mechanism described above will cause the emitter to be farther away from the gate, thereby weakening the surface electric field and reducing the emission efficiency. Summary of the invention

[0008] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a field emission X-ray tube with a movable emitter, which has a reserve function for the emitter and compensates for its damaged part by controlling the movement of the emitter, and increases the flexibility of regulating the beam of the ray tube.

[0009] To achieve the above object, the present invention provides a field emission X-ray tube with a movable emitter, comprising a vacuum maintenance assembly, a cathode assembly, an anode assembly, and a window assembly. 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 a movable control assembly, at least one emitter, a grid and a focusing electrode all mounted on the cathode base, each of the emitters comprises an emitter support column and an electron emitter fixedly connected, the cathode base, the grid and the focusing electrode are successively arranged along the emission direction of the electron beam, the end surface of the cathode base facing the grid is a shielding base surface, a support hole having one end extending to the shielding base surface is provided in the cathode base, the emitter support column is movably accommodated in the support hole, the part of the support hole located between the shielding base surface and the emitter support column constitutes an emitter storage cavity, the electron emitter comprises an emitter reserve section accommodated in the emitter storage cavity, and an emitter working section protruding from the shielding base surface, the movable control assembly is connected to the emitter support column, and drives the emitter support column and the electron emitter to move in a direction close to or away from the grid; The anode assembly comprises an anode base sealed and fixed in the vacuum chamber, and an anode target, wherein the anode base is provided with a bombardment inner cavity, and is provided with an electron beam incident hole and an X-ray outlet both connected to the bombardment inner cavity, the anode target is installed in the bombardment inner cavity, and the electron emitter is arranged opposite to the anode target via the electron beam incident hole; The window assembly is installed in the X-ray outlet.

[0010] Furthermore, the movement and regulation component comprises a displacement platform which can axially translate or axially extend in a direction approaching or moving away from the grid, and the emitter support column is fixed in the displacement platform.

[0011] Furthermore, when there are multiple emitters, the emitter support columns of the multiple emitters are fixed in the same displacement platform.

[0012] Furthermore, when there are multiple emitters, there are also multiple displacement platforms, which are fixedly connected to the emitter support columns of the multiple emitters in a one-to-one correspondence, and the axial translation or axial extension of the multiple displacement platforms are independently controlled.

[0013] Furthermore, the displacement platform is piezoelectric ceramic.

[0014] Furthermore, the vacuum maintaining assembly also includes an electrical feedthrough, which is sealed and fixed to one end of the shell close to the cathode assembly and is provided with a terminal. The cathode assembly also includes a piezoelectric ceramic base fixed to the cathode base, the emitter support column is movably inserted into the piezoelectric ceramic base, the piezoelectric ceramic is fixed on the piezoelectric ceramic base, and the piezoelectric ceramic base is provided with a first terminal electrically connected between the terminal and the piezoelectric ceramic.

[0015] Furthermore, the gate is a grid.

[0016] Furthermore, the grid is a plate component and is provided with electron beam through holes corresponding to the electron emitters one by one and allowing the electron beams to pass through.

[0017] Furthermore, the grid and the focusing electrode are two electrodes independent of each other, and the cathode assembly further comprises a first insulating member separated between the cathode base and the grid, and a second insulating member separated between the grid and the focusing electrode.

[0018] Furthermore, the grid and the focusing electrode are combined into one electrode, which is a grid-focusing-electrode multiplexing electrode, and the cathode assembly further includes a third insulating member separated between the cathode base and the grid-focusing-electrode multiplexing electrode.

[0019] Furthermore, the anode base includes an anode heat sink sealed and fixed to the outer shell, and an anode cap sealed and fixed to one end of the anode heat sink facing the cathode assembly, the bombardment cavity is formed between the anode heat sink and the anode cap, the anode target is fixed on the end face of the anode heat sink, and the electron beam incident hole and the X-ray outlet are both arranged on the anode cap.

[0020] As described above, the field emission X-ray tube with a movable emitter according to the present invention has the following beneficial effects.

[0021] In the present application, the mobile control component drives the emitter support column and the electron emitter to move in the direction of approaching or moving away from the grid, thereby controlling the length of the electron emitter protruding outward from the surface of the shielding base, that is, controlling the length of the working section of the emitter; in this way, the field emission X-ray tube with a movable emitter involved in the present application can at least achieve: 1. The part of the electron emitter contained in the emitter storage cavity can be in a lower electric field due to the shielding of the surface of the shielding base, and the probability of being destroyed by discharge is low, so it can be used as a reserve, so that the electron emitter has an emitter reserve section, which has a reserve function for the emitter; 2. When the electron emitter protrudes outward from the shielding base, the electron emitter can be placed in a lower electric field due to the shielding of the surface of the shielding base, and the probability of being destroyed by discharge is low, so the electron emitter can be used as a reserve, so that the electron emitter has an emitter reserve section, which has a reserve function for the emitter; 3. When the electron emitter protrudes outward from the shielding base, the electron emitter can be placed in a lower electric field due to the shielding of the surface of the shielding base, and the electron emitter can be placed in a lower electric field due to the shielding of the surface of the shielding base, and the probability of being destroyed by discharge is low, so the electron emitter can be used as a reserve, so that the electron emitter has an emitter reserve section, which has a reserve function for the emitter; 4. When the electron emitter protrudes outward from the shielding base, the electron emitter can be placed in a lower electric field due to the shielding of the surface of the shielding base, and ... After the emitter working section on the surface of the base has worked for a long time, or has been destroyed by a strong electric field, or has been gradually consumed, the electron emitter can be extended outward from the emitter storage cavity by moving the control component, thereby realizing the "regeneration" of the emitter working section, making up for its damaged and consumed part, and dynamically compensating the surface electric field of the electron emitter, so as to achieve stable emission again without replacing the field emission X-ray tube, thereby extending the service life of the field emission X-ray tube; 3. By moving the control component to control the length of the emitter working section, that is, adjusting the distance between the electron emitter surface and the grid, the purpose of increasing the flexibility of the ray tube beam control is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the structure of a field emission X-ray tube with a movable emitter in the present application.

[0023] Figure 2 for Figure 1 sectional view of .

[0024] Figure 3 This is a schematic structural diagram of a cathode assembly in a field emission X-ray tube with a movable emitter according to the present invention.

[0025] Figure 4 for Figure 3 sectional view of .

[0026] Figure 5 This is a schematic structural diagram of a cathode assembly in a field emission X-ray tube with a movable emitter according to the present invention.

[0027] Figure 6 for Figure 5 sectional view of .

[0028] Figure 7 This is a schematic structural diagram of the cathode assembly in the field emission X-ray tube with a movable emitter according to the third embodiment of the present invention.

[0029] Figure 8 for Figure 7 sectional view of .

[0030] Fig. 9This is a schematic structural diagram of a fourth embodiment of a cathode assembly in a field emission X-ray tube with a movable emitter of the present application.

[0031] Fig.10 for Fig. 9 sectional view of .

[0032] Fig.11 for Fig. 9 Schematic diagram of the electron trajectories in a field emission X-ray tube with a movable emitter.

[0033] Fig.12 for Fig. 9 Schematic diagram of the relationship between the target receiving current and the emitter working section length d of a field emission X-ray tube with a movable emitter.

[0034] Figures 13a to 13c for Fig.12 The pattern of the electron beam spot corresponding to the working section length d of different emitters.

[0035] Fig.14 This is a schematic structural diagram of Embodiment 1 of the anode assembly in a field emission X-ray tube with a movable emitter of the present application.

[0036] Fig.15 This is a schematic structural diagram of the second embodiment of the anode assembly in the field emission X-ray tube with a movable emitter of the present application.

[0037] Above Figures 5 to 11 In the figure, part of the cathode base and the insulating parts are omitted. DETAILED DESCRIPTION

[0038] 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.

[0039] 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, without affecting the effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical content disclosed 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.

[0040] 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.

[0041] 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.

[0042] 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 with a movable emitter. Figure 1 and 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 a movable emitter provided by the present invention comprises a vacuum maintenance assembly 10, a cathode assembly 20, an anode assembly 30 and a window assembly 40.

[0043] 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.

[0044] like Figure 1 and Figure 2As shown, the cathode assembly 20 includes a cathode base 21, a movable control assembly, at least one emitter 22, a grid 23 and a focusing electrode 24. The cathode base 21 is sealed and fixed in the vacuum chamber 12 of the housing 11. The movable control assembly, at least one emitter 22, the grid 23 and the focusing electrode 24 are all installed on the cathode base 21. Each emitter 22 includes an emitter support column 25 and an electron emitter 26 fixed to the end of the emitter support column 25. The emitter support column 25 and the electron emitter 26 both extend straight up and down along the axial direction of the field emission X-ray tube. The electron emitter 26 is used to emit electron beams downward; the cathode base 21, the grid 23 and the focusing electrode 24 are arranged in sequence from top to bottom along the emission direction of the electron beam. In particular, the lower end surface of the cathode base 21 facing the grid 23 is the shielding base surface 201, and an axially extending support hole 202 is provided in the cathode base 21. At least the lower end of the support hole 202 passes through the cathode base 21 downward, that is, the lower end of the support hole 202 extends downward to the shielding base surface 201. The emitter support column 25 can be axially movably accommodated in the support hole 202, and the part of the support hole 202 located between the shielding base surface 201 and the emitter support column 25 constitutes an emitter storage cavity 203; the electron emitter The electron emitter 26 has a part in the emitter storage cavity 203 and hidden in the shielding base surface 201, and a part extends outward from the emitter storage cavity 203 and protrudes outward from the shielding base surface 201. The part of the electron emitter 26 accommodated in the emitter storage cavity 203 is defined as the emitter storage section 261, and the part of the electron emitter 26 protruding outward from the shielding base surface 201 is defined as the emitter working section 262. The emitter working section 262 extends axially downward from the lower end of the emitter storage section 261. The moving control component is connected to the emitter support column 25, and is used to drive the emitter support column 25 and the electron emitter 26 to move axially in the direction of approaching or moving away from the gate 23.

[0045] like Figure 1 and Figure 2 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 the lower end of the vacuum chamber 12 along the emission direction of the electron beam in the cathode assembly 20. A bombardment cavity 311 is provided in the anode base 31, and an electron beam incident hole 312 and an X-ray outlet 313 are provided, both of which are connected to the bombardment cavity 311. The anode target 32 ​​is installed in the bombardment cavity 311 at a set inclination angle. The electron emitter 26 is arranged opposite to the anode target 32 ​​through the electron beam incident hole 312. 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.

[0046] During operation, the field emission X-ray tube with the movable emitter mentioned above applies voltage to the grid 23, so that the emitter working section 262 of the electron emitter 26 emits an electron beam, and 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, thereby limiting the electron trajectory 50; 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 are guided to the desired workpiece after passing through the window assembly 40. By adjusting the voltage of the grid 23 and the focusing electrode 24, the size of the X-ray focal spot focused on the anode target 32 ​​can be adjusted.

[0047] The electron emitter 26 in the present application can move axially, and the axial displacement of the emitter support column 25 and the electron emitter 26 is controlled by moving the control component, thereby controlling the length d of the electron emitter 26 protruding outward from the shielding base surface 201, that is, controlling the length d of the emitter working section 262, or adjusting the distance between the lower end of the emitter working section 262 and the shielding base surface 201, and a part of the electron emitter 26 is accommodated in the cathode base 21. Based on the characteristics of the adjustable and stored axial displacement of the electron emitter 26 in the present application, the field emission X-ray tube with a movable emitter involved in the present application has at least the following advantages.

[0048] 1. The electron emitter 26 contained in the emitter storage cavity 203 can be in a lower electric field due to the electric field shielding of the shielding base surface 201, and the probability of being destroyed by discharge is low, so it can be used as a reserve, so that the electron emitter 26 has an emitter reserve section 261 contained in the cathode base 21, which has a reserve function for the emitter.

[0049] 2. The emitter working section 262 protruding from the surface 201 of the shielding base emits electron beams under a strong electric field. When the emitter working section 262 protruding from the surface 201 of the shielding base works for a long time or is destroyed by a strong electric field, the electron emitter 26 is extended outward from the emitter storage cavity 203 by moving the regulating component to form a new emitter working section 262, thereby realizing the "regeneration" of the emitter working section 262 and compensating for its damaged part; the new emitter working section 262 is moved to the working position again, realizing stable emission again without replacing the field emission X-ray tube, thereby extending the service life of the field emission X-ray tube.

[0050] 3. When the emitter working section 262 protruding from the surface of the shielding base 201 is modified by the electric field and changes slowly, the emitter working section 262 is gradually consumed, causing the distance between the lower end of the emitter working section 262 and the gate 23 to increase, resulting in a decrease in the surface electric field of the emitter working section 262, resulting in a decrease in emission efficiency; at this time, the electron emitter 26 is extended outward from the emitter storage cavity 203 by moving the regulating component to compensate for its consumed part, that is, dynamically compensate for the distance between the emitter working section 262 and the gate 23, thereby dynamically compensating for the surface electric field of the electron emitter 26, ensuring the emission efficiency and making the emission stable.

[0051] 4. The traditional method of adjusting the electron beam current by regulating the voltage of the gate 23 will change the overall magnification of the system while changing the current size, thereby changing the focal spot size and affecting subsequent work requirements. However, the present application adjusts the length d of the emitter working section 262 by moving the regulating component, that is, adjusting the distance between the surface of the electron emitter 26 and the gate 23, which can dynamically change the emission current and adjust the beam size, thereby achieving the purpose of increasing the flexibility of the beam current regulation of the ray tube. The method of adjusting the electron beam current by adjusting the axial position of the electron emitter 26 involved in the present application has little effect on the overall magnification of the system, resulting in a small change in the focal spot. Therefore, in addition to the traditional mode of adjusting the voltage of the gate 23 to adjust the beam current of the ray tube, the present application provides a new supplement for the control of the current of the field effect electron emitter 26.

[0052] The structures of the vacuum maintaining assembly 10, the cathode assembly 20, the anode assembly 30 and the window assembly 40 of the field emission X-ray tube are described below.

[0053] Vacuum maintenance component 10: Figure 1 and Figure 2 As shown, in addition to the housing 11, the vacuum maintenance assembly 10 also includes an electrical feedthrough 13, which is sealed and fixed to the upper end of the housing 11 near the cathode assembly 20. The electrical feedthrough 13 is provided with a terminal 14. The electrical feedthrough 13 realizes the transmission of electrical signals inside and outside the housing 11, while ensuring the sealing of the vacuum environment. The field emission X-ray tube can be an open tube structure or a closed tube structure. The material of the housing 11 can be, but is not limited to, any one or more combinations of glass, ceramics, and metals to achieve the required vacuum degree.

[0054] Cathode assembly 20: The movable control assembly for controlling the axial displacement of the electron emitter 26 can be mechanically driven, electrically driven, or magnetic field driven; only one emitter 22 can be provided, or multiple emitters can be provided; the gate 23 and the focusing electrode 24 can be two independent electrodes, or a common electrode; in this way, the cathode assembly 20 has multiple embodiments.

[0055] Cathode assembly 20 embodiment 1, as Figure 3 and Figure 4 As shown, the emitter 22 is provided with one. The mobile control component includes a displacement platform 27 that can be axially extended and retracted in the direction close to or away from the gate 23, and the emitter support column 25 is fixed in the displacement platform 27. Preferably, the displacement platform 27 is a piezoelectric ceramic 28. Based on this, the cathode assembly 20 also includes a piezoelectric ceramic base 29 fixed to the cathode base 21, the upper section of the emitter support column 25 can be movably arranged in the piezoelectric ceramic base 29 up and down, and the lower section of the emitter support column 25 can be movably arranged in the support hole 202 of the cathode base 21 up and down, and the support hole 202 is a through hole structure. The piezoelectric ceramic 28 is fixed on the lower end surface of the piezoelectric ceramic base 29, and the piezoelectric ceramic base 29 is provided with a first terminal, which is electrically connected between the terminal 14 of the electrical feedthrough 13 and the piezoelectric ceramic 28, and the piezoelectric ceramic base 29 is used for fixing the piezoelectric ceramic 28 and driving the electrical signal. When the piezoelectric ceramic 28 is energized, the piezoelectric effect causes the piezoelectric ceramic 28 to move axially, causing the emitter support column 25 to move axially, thereby controlling the electron emitter 26 to move along the Figure 4 The electron emitter 26 is precisely displaced in the longitudinal direction to adjust the distance of the electron emitter 26 protruding from the shielding base surface 201, that is, to adjust the length d of the emitter working section 262, to compensate for the damaged and consumed part of the emitter working section 262, or to dynamically adjust the distance between the electron emitter 26 and the gate 23.

[0056] Furthermore, a second terminal is provided on the cathode base 21 , and the second terminal is electrically connected to the terminal 14 of the electrical feed-through 13 for transmitting electrical signals, such as grounding the cathode base 21 .

[0057] Furthermore, if Figure 3 and Figure 4As shown, the grid 23 and the focusing electrode 24 are two independent electrodes, and the potential of the grid 23 and the potential of the focusing electrode 24 can be independently controlled, so that the grid 23 and the focusing electrode 24 have different potentials, or the grid 23 and the focusing electrode 24 have the same potential. Combined with the adjustment of the length d of the emitter working section 262, the size of the electron beam spot can be adjusted more flexibly. For example, by independently adjusting the voltage of the focusing electrode 24, an X-ray focal spot that meets the working requirements can be formed, and the electron beam can be accurately focused on the target material of the anode target 32. Then, these X-rays pass through the window assembly 40 and finally irradiate the workpiece to be processed. Preferably, the cathode assembly 20 also includes a first insulating member 210 separating the cathode base 21 and the gate 23, and a second insulating member 211 separating the gate 23 and the focusing electrode 24; the first insulating member 210 provides insulation for the cathode base 21 and the gate 23, and accurately controls the distance between the electron emitter 26 and the gate 23; the second insulating member 211 provides electrical isolation for the gate 23 and the focusing electrode 24, and accurately regulates the distance between the gate 23 and the focusing electrode 24.

[0058] The difference between the second embodiment of the cathode assembly 20 and the first embodiment of the cathode assembly 20 is that: Figure 5 and Figure 6 As shown, there are multiple emitters 22. In this embodiment, there are five emitters 22, which are respectively defined as a first emitter 221, a second emitter 222, a third emitter 223, a fourth emitter 224 and a fifth emitter 225. The first emitter 221, the second emitter 222, the third emitter 223, the fourth emitter 224 and the fifth emitter 225 all include an emitter support column 25 and an electron emitter 26 fixed to the lower end of the emitter support column 25. The spacing between the first emitter 221, the second emitter 222, the third emitter 223, the fourth emitter 224 and the fifth emitter 225 is controlled, which can effectively avoid electric field shielding between the electron emitters 26. The cathode assembly 20 embodiment 2 also includes a first insulating member 210 separated between the cathode base 21 and the gate 23, and a second insulating member 211 separated between the gate 23 and the focusing electrode 24, but the first insulating member 210 and the second insulating member 211 are in Figure 5 and Figure 6 Not shown.

[0059] like Figure 5 and Figure 6As shown, the mobile control component includes a displacement platform 27 that can be axially translated in a direction close to or away from the gate 23, and the emitter support columns 25 of the first emitter 221, the second emitter 222, the third emitter 223, the fourth emitter 224 and the fifth emitter 225 are fixed in the same displacement platform 27. Preferably, the displacement platform 27 is supported in the support hole 202 of the cathode base 21 so as to be movable up and down. The mobile control component also includes a mobile control driving source and a mobile control transmission unit. The mobile control driving source is connected to the displacement platform 27 through the mobile control transmission unit, and drives the displacement platform 27 to move axially, thereby driving the emitter support columns 25 of multiple emitters 22 to move up or down synchronously, so as to achieve the synchronous movement of multiple electron emitters 26. Therefore, the second embodiment of the cathode assembly 20 is a distributed integrally movable emitter 22 structure. The mobile control driving source can be a servo motor, a stepping motor, or an electromagnet, and the mobile control transmission unit can be a ball screw transmission structure, a gear rack transmission structure, or a screw nut transmission structure.

[0060] The cathode assembly 20 of the second embodiment can regulate the current of the field emission X-ray tube as a whole. When there is a large demand for current, the displacement platform 27 is driven to move downward toward the grid 23, the extension length d of the multiple electron emitters 26 from the cathode base 21 is increased, and the distance between the multiple electron emitters 26 and the grid 23 is shortened, so that the surface electric field increases and the emission beam increases. Conversely, when there is a small demand for current, the displacement platform 27 is driven to move upward away from the grid 23, the extension length d of the multiple electron emitters 26 from the cathode base 21 is reduced, and the distance between the multiple electron emitters 26 and the grid 23 is increased, so that the surface electric field decreases and the emission beam decreases. In addition, after all the electron emitters 26 have been working for a long time, they may be consumed or damaged. By regularly adjusting the downward displacement of the displacement platform 27, the extension length d of the multiple electron emitters 26 from the cathode base 21 can be regularly adjusted to ensure the "regeneration" of the emitter working section 262 of the multiple electron emitters 26, so that the multiple electron emitters 26 can work normally again, and the service life of the field emission X-ray tube is extended.

[0061] The third embodiment of the cathode assembly 20 is different from the first embodiment of the cathode assembly 20 in that: Figure 7 and Figure 8As shown, there are multiple emitters 22. In this embodiment, there are four emitters 22, which are respectively defined as a sixth emitter 226, a seventh emitter 227, an eighth emitter 228 and a ninth emitter 229. The sixth emitter 226, the seventh emitter 227, the eighth emitter 228 and the ninth emitter 229 all include an emitter support column 25 and an electron emitter 26 fixed to the lower end of the emitter support column 25. The spacing between the sixth emitter 226, the seventh emitter 227, the eighth emitter 228 and the ninth emitter 229 is controlled, which can effectively avoid electric field shielding between the electron emitters 26. The cathode assembly 20 embodiment 3 also includes a first insulating member 210 separated between the cathode base 21 and the gate 23, and a second insulating member 211 separated between the gate 23 and the focusing electrode 24, but the first insulating member 210 and the second insulating member 211 are in Figure 7 and Figure 8 Not shown.

[0062] like Figure 7 and Figure 8 As shown, the electron emitters 26 of the sixth emitter 226, the seventh emitter 227, the eighth emitter 228 and the ninth emitter 229 are all fixed in a piezoelectric ceramic 28 constituting a displacement platform 27, and the cathode assembly 20 embodiment 3 includes four groups of piezoelectric ceramic bases 29 and piezoelectric ceramics 28, and each group of piezoelectric ceramic bases 29 and piezoelectric ceramics 28 independently corresponds to an emitter 22. Therefore, the cathode assembly 20 embodiment 3 is a distributed, independently movable emitter 22 structure, and the emitter support columns 25 of multiple emitters 22 are respectively fixed in a displacement platform 27, and the axial translation or axial extension of multiple displacement platforms 27 is independently controlled. The sixth emitter 226, the seventh emitter 227, the eighth emitter 228 and the ninth emitter 229 have independent electrical connections, and are equipped with independent mobile control components, which can independently control the power-on voltage of each piezoelectric ceramic 28, and also independently control the extension amount of each piezoelectric ceramic 28, thereby independently controlling the axial displacement amount of each electron emitter 26. Based on the characteristic that the electron emitter 26 of each emitter 22 in the third embodiment of the cathode assembly 20 independently controls the axial displacement, the third embodiment of the cathode assembly 20 has the following advantages.

[0063] 1. It has a longer service life and can work for a relatively longer time; when there is an emitter 22 with a damaged electron emitter 26, it is only necessary to control the piezoelectric ceramic 28 connected to the emitter 22 to be energized, so that the electron emitter 26 of the emitter 22 extends from the shielding base surface 201, so that the electron emitter 26 of the emitter 22 works again, while the other emitters 22 remain in their original state. In this way, frequent replacement of the field emission X-ray tube is avoided, and the service life of the field emission X-ray tube is effectively extended.

[0064] 2. The axial movement of the electron emitters 26 of the multiple emitters 22 can be independently controlled, so that the length d of each electron emitter 26 protruding from the shielding base surface 201 can be independently controlled, that is, the length d of the emitter working section 262 of each electron emitter 26 can be independently controlled, so as to control the emission current in real time, and achieve the effect of controlling the overall beam current and the overall focal spot. For example: the electron emitters 26 of the sixth emitter 226, the seventh emitter 227 and the eighth emitter 228 are all retracted into the shielding base surface 201, and only the electron emitter 26 of the ninth emitter 229 is left protruding from the shielding base surface 201, then only the electron emitter 26 of the ninth emitter 229 is working, and a smaller source size can be obtained. When the voltage of the focusing electrode 24 and the anode assembly 30 remains unchanged, the magnification of the system remains unchanged, and the focal spot can be effectively reduced by adjusting the working state of each electron emitter 26. For another example: the electron emitters 26 of the sixth emitter 226, the seventh emitter 227, the eighth emitter 228 and the ninth emitter 229 are all extended out of the shielding base surface 201, so that the electron emitters 26 of the four emitters 22 are all working, which increases the emission beam current exponentially, which is very suitable for high current density applications.

[0065] 3. In actual applications, the focal spot may have a phenomenon of local photon non-uniformity, which will cause contrast artifacts in the corresponding detection instrument and cause misdiagnosis. The cathode assembly 20 embodiment 3 can independently change the length d of the electron emitter 26 of each emitter 22 protruding from the shielding base surface 201 according to the intensity of the focal spot at different positions; the electron emitter 26 corresponding to the area with higher focal spot intensity is processed to reduce the length d of its protrusion from the shielding base surface 201; the electron emitter 26 corresponding to the area with insufficient photon intensity is processed to increase the length d of its protrusion from the shielding base surface 201, so as to make the overall photon intensity uniform.

[0066] The fourth embodiment of the cathode assembly 20 is different from the first embodiment of the cathode assembly 20 in that: Fig. 9 and Fig.10 As shown, the grid 23 and the focusing electrode 24 are combined into one electrode, or the grid 23 and the focusing electrode 24 share one electrode, which is the grid-focusing electrode multiplexing electrode 213. The cathode assembly 20 also includes a third insulating member 212 separated between the cathode base 21 and the grid-focusing electrode multiplexing electrode 213. In the fourth embodiment of the cathode assembly 20, since the grid 23 and the focusing electrode 24 adopt an integrated structure, the same potential is applied to the two, so that the position of the electron emitter 26 plays a decisive role in the regulation of the electron beam current.

[0067] In this embodiment, the electron emitter 26 is a carbon nanotube with a diameter of 0.1 mm. Non-essential parts are removed and the electron trajectory 50 is obtained by simulation using electronic optical simulation software. Fig.11 As shown. Fig.11 It can be seen that: the electron beam is emitted from the carbon nanotube, passes through the gate 23, and some of the blocked electrons 60 are cut off by the gate focusing electrode multiplexing electrode 213, and the unblocked electrons are focused by the gate focusing electrode multiplexing electrode 213 and converge on the anode target 32. When the length d of the electron emitter 26 protruding from the shielding base surface 201 is changed, the current on the anode target 32 ​​changes. The relationship between the current change on the anode target 32 ​​and the length d of the electron emitter 26 protruding from the shielding base surface 201 is as follows: Fig.12 As shown, the light spot sizes corresponding to different lengths d of the electron emitter 26 protruding from the shielding base surface 201 are as follows: Fig.13a , Fig.13b and Fig.13c As shown, Fig.13a , Fig.13b and Fig.13c The horizontal and vertical coordinates in are two perpendicular radial directions of the field emission X-ray tube. Specifically: Fig.13a is the light spot when the length d=0 mm of the electron emitter 26 protruding from the shielding base surface 201, Fig.13b is the light spot when the length d=0.06 mm of the electron emitter 26 protruding from the shielding base surface 201, Fig.13c The light spot is when the length d of the electron emitter 26 protruding from the surface 201 of the shielding base is 0.12 mm. Obviously, as the length d of the electron emitter 26 protruding from the surface 201 of the shielding base increases, the beam current gradually increases. When the length d is 0.12 mm, the current on the anode target 32 ​​changes from about 5 mA to about 27 mA, and the beam gain of the field emission X-ray tube is more than five times. However, when the length d of the electron emitter 26 protruding from the surface 201 of the shielding base gradually increases, the electron emitter 26 gradually approaches the gate 23, the emission current increases, and due to the space charge effect, the light spot size only increases slightly. That is, by increasing the length d of the electron emitter 26 protruding from the surface 201 of the shielding base, the current increases by about five times, but the overall size of the electron beam spot does not change dramatically, which is consistent with the effect described above.

[0068] Furthermore, in the four embodiments of the cathode assembly 20, the electron emitter 26 is a field emission electron source, which can be a cold field emission electron source or a thermal field emission electron source. The electron emitter 26 and the emitter support column 25 can be fixed in a manner that is not limited to: direct growth of the electron emitter 26, welding, bonding, fusion, mechanical extrusion, or a combination of multiple fixing methods, such as: forming the electron emitter 26 by coating an emission material on the emitter support column 25.

[0069] Further, in the four embodiments of the cathode assembly 20, the grid 23 can be a grid. More preferably, the grid 23 is a plate component and is provided with an electron beam through hole corresponding to the electron emitter 26 and allowing the electron beam to pass through. In this case, the grid 23 can be a single-layer structure or a multi-layer structure. For example, the grid 23 includes an insulating layer, a conductive layer and a shielding layer stacked in sequence, and the layers of the grid 23 are fixed together by welding or hydraulic forming. After the grid 23 adopts the small hole structure of the electron beam through hole, it not only ensures the electric field on the surface of the electron emitter 26, but also guides the field emission electrons; in addition, these small hole designs corresponding to the electron emitter 26 can also help reduce the situation where the grid 23 is bombarded by electrons, thereby reducing the risk of deformation or damage of the grid 23 due to electron impact. The shape of the electron beam through hole can be circular, square, diamond, or other regular shapes, and the processing method of the electron beam through hole can be but is not limited to laser processing, electrochemical processing, micro-electrodischarge processing, ultrasonic processing, electronic processing and ion beam processing.

[0070] Anode assembly 30: The anode assembly 30 is also provided with a structure for dissipating heat for the anode target 32. The heat dissipation structure may be a water-cooled heat dissipation structure or a high thermal conductivity material for dissipating heat. Thus, the anode assembly 30 has multiple embodiments.

[0071] Anode assembly 30 embodiment 1, as Fig.14 As shown, the anode base 31 includes an anode heat sink 33 sealed and fixed to the housing 11, and an anode cap 34 sealed and fixed to the anode heat sink 33 facing the upper end of the cathode assembly 20, a bombardment cavity 311 is formed between the anode heat sink 33 and the anode cap 34, the anode target 32 ​​is fixed to the upper end surface of the anode heat sink 33 by welding or casting, and the electron beam incident hole 312 and the X-ray outlet 313 are both arranged on the anode cap 34. The anode heat sink 33 is made of a high thermal conductivity material, such as copper. The anode assembly 30 embodiment 1 has a simple structure and can effectively dissipate heat for the anode target 32.

[0072] Anode assembly 30 embodiment 2, as Fig.15As shown, the second embodiment of the anode assembly 30 further includes a target base 35 and a cooling assembly, the anode base 31 includes a base cap 361, a base neck 362 and a base column 363 connected in sequence from top to bottom, the electron beam incident hole 312 is provided on the base neck 362, the bombardment cavity 311 is formed between the base neck 362 and the base column 363, and the X-ray outlet 313 is provided on the base column 363. The target base 35 is fixedly arranged in the base column 363 of the anode base 31 by welding or casting, and the anode target 32 ​​is fixed on the upper end surface of the target base 35 facing the bombardment cavity 311. The cooling assembly includes a medium inlet 37 penetrating the base column 363 of the anode base 31 and the target base 35, a cooling cavity 351 provided in the target base 35, and a medium outlet 38 penetrating the base column 363 of the anode base 31 and the target base 35, and the medium inlet 37 and the medium outlet 38 are both connected to the cooling cavity 351. A cooling medium such as cooling water or cooling oil flows into the cooling cavity 351 through the medium inlet 37, and then flows out through the medium outlet 38, and circulates in the cooling cavity 351, effectively dissipating heat from the target base 35 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, such as copper, to achieve efficient heat dissipation.

[0073] In the two embodiments of the anode assembly 30, the anode base 31 is sealed and fixed at the lower end of the housing 11 by welding and sintering to ensure the overall vacuum degree of the field emission X-ray tube. Figure 1 As shown, the lower end of the housing 11 is connected to an anode connection part 70 by welding, sintering or bonding, and the anode connection part 70 is fixedly connected to the outer periphery of the anode base 31 by brazing, laser welding or physical pressing to ensure sealing. In addition, 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 ​​is a tungsten target, a copper target, a molybdenum target, a rhenium target, a rhodium target, a chromium target, a gold target, a silver target, a platinum target, an iron target, a titanium target, a SIC target, etc. or a combination thereof, and the target material of the anode target 32 ​​is determined according to the energy requirements of the X-ray. After the heat is dissipated, the anode target 32 ​​is guaranteed not to be ablated, which effectively guarantees the stability and service life of the field emission X-ray tube.

[0074] Window assembly 40: The window assembly 40 is preferably made of beryllium or diamond sheets to filter out low-energy electrons, reduce the heat dissipation burden of the anode target 32, and also reduce the amount of X-ray filtering. The window assembly 40 is fixed in the X-ray outlet 313 of the anode base 31 by welding or casting.

[0075] In summary, the field emission X-ray tube with a movable emitter according to the present invention has at least the following beneficial effects.

[0076] The field emission X-ray tube of the present invention places the electron emitters 26 contained in the emitter storage cavity 203 under a relatively low electric field, so that the probability of them being destroyed by discharge is relatively low, thereby having a reserve effect on the electron emitters 26 .

[0077] The field emission X-ray tube of the present invention controls the axial displacement of the electron emitter 26 to "regenerate" the emitter working section 262 of the electron emitter 26, thereby extending the service life of the field emission X-ray tube.

[0078] The field emission X-ray tube of the present invention dynamically changes the emission current and adjusts the beam size by regulating the axial displacement of the electron emitter 26, thereby increasing the control flexibility of the beam of the ray tube and preventing excessive changes in the focal spot.

[0079] In summary, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0080] 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 movable 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), and a movable control assembly, at least one emitter (22), a grid (23) and a focusing electrode (24) all mounted on the cathode base (21); each of the emitters (22) comprises an emitter support column (25) and an electron emitter (26) that are fixedly connected; the cathode base (21), the grid (23) and the focusing electrode (24) are arranged in sequence along the emission direction of the electron beam; the end surface of the cathode base (21) facing the grid (23) is a shielding base surface (201); and the cathode base (21) has an end extending to the shielding base surface (202). 01), the emitter support column (25) being movably accommodated in the support hole (202), the portion of the support hole (202) located between the shielding base surface (201) and the emitter support column (25) constituting an emitter storage cavity (203), the electron emitter (26) comprising an emitter storage section (261) accommodated in the emitter storage cavity (203), and an emitter working section (262) protruding outward from the shielding base surface (201), the movement control component being connected to the emitter support column (25) and driving the emitter support column (25) and the electron emitter (26) to move in a direction approaching or away from the gate (23); The anode assembly (30) comprises an anode base (31) sealed and fixed in a vacuum chamber (12), and an anode target (32); a bombardment cavity (311) is provided in the anode base (31), and an electron beam entrance hole (312) and an X-ray outlet (313) both of which are in communication with the bombardment cavity (311); the anode target (32) is installed in the bombardment cavity (311); and the electron emitter (26) is arranged opposite to the anode target (32) via the electron beam entrance hole (312); The window assembly (40) is installed in the X-ray outlet (313).

2. The field emission X-ray tube with a movable emitter according to claim 1, characterized in that: The mobile control component comprises a displacement platform (27) capable of axial translation or axial extension in a direction approaching or moving away from the grid (23), and the emitter support column (25) is fixed in the displacement platform (27).

3. The field emission X-ray tube with a movable emitter according to claim 2, characterized in that: When there are multiple emitters (22), the emitter support columns (25) of the multiple emitters (22) are fixed in the same displacement platform (27).

4. The field emission X-ray tube with a movable emitter according to claim 2, characterized in that: When there are multiple emitters (22), there are also multiple displacement platforms (27), which are fixedly connected to the emitter support columns (25) of the multiple emitters (22) in a one-to-one correspondence, and the axial translation or axial extension of the multiple displacement platforms (27) are independently controlled.

5. The field emission X-ray tube with a movable emitter according to any one of claims 2 to 4, characterized in that: The displacement platform (27) is a piezoelectric ceramic (28).

6. The field emission X-ray tube with a movable emitter according to claim 5, characterized in that: The vacuum maintaining assembly (10) further comprises an electrical feedthrough (13), the electrical feedthrough (13) being sealed and fixed to one end of the housing (11) close to the cathode assembly (20) and provided with a terminal (14), the cathode assembly (20) further comprises a piezoelectric ceramic base (29) fixed to the cathode base (21), the emitter support column (25) being movably inserted into the piezoelectric ceramic base (29), the piezoelectric ceramic (28) being fixed on the piezoelectric ceramic base (29), and the piezoelectric ceramic base (29) being provided with a first terminal electrically connected between the terminal (14) and the piezoelectric ceramic (28).

7. The field emission X-ray tube with a movable emitter according to claim 1, characterized in that: The grid (23) is a grid.

8. The field emission X-ray tube with a movable emitter according to claim 1, characterized in that: The grid (23) is a plate component and is provided with electron beam through holes which correspond one-to-one to the electron emitters (26) and allow the electron beam to pass through.

9. The field emission X-ray tube with a movable emitter according to claim 1, characterized in that: The grid (23) and the focusing electrode (24) are two electrodes independent of each other, and the cathode assembly (20) further comprises a first insulating member (210) separated between the cathode base (21) and the grid (23), and a second insulating member (211) separated between the grid (23) and the focusing electrode (24).

10. The field emission X-ray tube with a movable emitter according to claim 1, characterized in that: The grid (23) and the focusing electrode (24) are combined into one electrode, which is a grid-focusing-electrode multiplexing electrode (213). The cathode assembly (20) further comprises a third insulating member (212) separated between the cathode base (21) and the grid-focusing-electrode multiplexing electrode (213).

11. The field emission X-ray tube with a movable emitter according to claim 1, characterized in that: The anode base (31) comprises an anode heat sink (33) sealed and fixed to the housing (11), and an anode cap (34) sealed and fixed to one end of the anode heat sink (33) facing the cathode assembly (20); the bombardment cavity (311) is formed between the anode heat sink (33) and the anode cap (34); the anode target (32) is fixed to the end surface of the anode heat sink (33); and the electron beam incident hole (312) and the X-ray outlet (313) are both arranged on the anode cap (34).

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