KR102095268B1 - Field Emission X-Ray Source Device - Google Patents

Abstract

Disclosed is a field emission X-ray source device configured to prevent defects such as shortened lifespan and focal spot fluctuations due to a decrease in vacuum in the aging process. The field emission X-ray source device according to the present invention includes an electron emission source disposed on a cathode electrode on one side of a vacuum container, and an anode electrode disposed opposite to each other with a space between the electron emission source and vacuum on the other side of the vacuum container. Including, the anode electrode, being hit by the electron beam emitted from the electron emission source to provide a target surface inclined with respect to the direction in which the electron beam travels, and a body connected to the hitting part A target member having a coupling portion formed in a direction away from the target surface; And an anode electrode body made of a conductor having higher thermal conductivity than the target member and mechanically coupled to the coupling portion.

Description

Field Emission X-Ray Source Device

Field of the Invention The present invention relates to a field emission X-ray source device, and more particularly, to a field emission X-ray source device that emits X-rays by colliding accelerated electrons emitted from an electron emission source on the cold cathode side to a target on the anode electrode side. .

In general, a conventional X-ray source device used in a medical institution for diagnosis of a disease uses a hot cathode made of tungsten as an electron emission source for generating X-rays, and heats tungsten filament with high voltage to emit electrons and anode the emitted electrons. It is structured to generate X-rays by colliding with the target on the electrode side.

However, the tungsten filament-based hot cathode X-ray source device consumes a lot of power to generate electrons, and since the generated electrons are randomly emitted from a tungsten surface having a spiral structure, X-ray emission efficiency is extremely low. In addition, an interval of a certain time is required for heating and cooling of the tungsten filament, and it is difficult to emit X-rays in the form of pulses.

In order to solve the problems of the conventional hot cathode X-ray source device, recently, research on X-ray source devices using nanostructures such as carbon nanotubes (CNT) as a cold cathode electron emission source has been actively conducted. Unlike the conventional tungsten filament-based hot cathode X-ray source device, the X-ray source device using carbon nanotubes has an electron emission mechanism that is an electric field emission method, and is different from the conventional thermal electron emission method. The carbon nanotube-based X-ray source device can emit electrons by applying a lower voltage than the tungsten filament-based hot cathode X-ray source device, and because the emitted electrons are emitted along the longitudinal direction of the carbon nanotube, the target on the anode electrode side X-ray emission efficiency is very high due to the excellent directivity of electrons toward the beam. In addition, since it is easy to emit pulsed X-rays, it is possible to acquire X-ray images at low doses, and it is possible to shoot X-ray videos, so it is very likely to be used for dental treatment such as dental implant examination.

Field emission X-ray sources, which have been hitherto known, have an electron emitter installed on a cathode electrode and a gate electrode installed adjacent to the cathode, in a vacuum container. It is configured to emit electrons by an electric field formed between electron emission sources. The gate electrode has a shape of a mesh or a metal plate in which a plurality of holes are arranged according to an arrangement of electron emission sources. When an electron beam emitted from an electron emitter proceeds through such a mesh structure or a plurality of holes, electrons can be several to several tens of kV by an electric field formed between an anode and a cathode. Acceleration to the X-ray target (target) installed on the anode side, so that the X-rays are emitted. Meanwhile, one or more focusing electrodes are added between the anode electrode and the gate electrode so that the electron beam is focused to a region of the anode electrode. In order to operate the field emission X-ray source device, a positive gate voltage is applied to the gate electrode based on the potential of the cathode electrode, and a positive acceleration voltage is applied to the anode electrode. At this time, a voltage for focusing the electron beam is applied to the focusing electrode, and the voltage applied to the focusing electrode may be changed according to an operating condition.

Conventional X-ray sources, including field emission X-ray sources previously developed so far, have been bonded to the surface of the anode electrode through a brazing (Brazing) plate-shaped X-ray target. However, such an X-ray target bonded by brazing causes a defect to occur during the aging process of the field emission X-ray source device. During aging, high temperature occurs because the electron beam collides with the X-ray target for a long time. At this time, due to the high temperature generated, some of the brazing filler melts and the position of the target causes fluctuations in the focal spot or changes in the brazing filler. This is because the degree of vacuum is inhibited by outgasing.

Therefore, the present invention has been proposed to solve the above-mentioned problems, and by improving the coupling method and structure between the anode electrode and the X-ray target, the fluctuation of the focal spot in the field emission X-ray source device or the degree of vacuum decreases. The purpose is to eliminate the cause of such defects.

In order to solve the above problems, the field emission X-ray source device according to the present invention, between the electron emission source disposed on the cathode electrode on one side of the vacuum container, and the space between the electron emission source and the vacuum on the other side of the vacuum container. An anode electrode disposed to face each other, and the anode electrode is a striking unit that provides a target surface inclined with respect to a direction in which the electron beam travels by being hit by an electron beam emitted from the electron emission source. A target member having a coupling part formed in one body with the striking part and extending in a direction away from the target surface; And an anode electrode body made of a conductor having higher thermal conductivity than the target member and mechanically coupled to the coupling portion.

The target member and the anode electrode body may include mechanical coupling structures corresponding to each other so that other materials are not directly interposed therebetween and are in direct contact with each other to be coupled.

The mechanical coupling structure may include a screw coupling structure, a protrusion-groove coupling structure, a key coupling structure, or a bolt coupling structure between the coupling portion and the anode electrode body.

In addition, the target member and the anode electrode body may be fusion-welded through a filler-free welding so as to be in direct contact with each other.

The field emission X-ray source device according to the present invention is disposed on the opposite side of the target member on the anode electrode body, and is joined to one end of the vacuum container so that the anode electrode is not exposed outside the vacuum container. It may further include a heat sink.

At this time, the heat sink of the non-conductive material may include a base and a radiating fin formed integrally with alumina ceramics. The non-conductive heat sink may further include a metal block disposed between the inside of the base and the anode electrode body.

Field emission X-ray source device according to another aspect of the present invention, an electron emission source disposed on the cathode electrode on one side of the vacuum container; On the other side of the vacuum container, the electron emission source and the vacuum space are disposed to face each other, and a target surface inclined with respect to the direction of the electron beam traveling by being hit by the electron beam emitted from the electron emission source An anode electrode having a target member provided; And a heat sink made of a non-conductive material that is joined to the anode electrode side end of the vacuum container so that the anode electrode coupled to the inside thereof is not exposed outside the vacuum container.

As described above, according to the present invention, by improving the coupling method and the structure between the anode electrode and the X-ray target, the effect of removing factors of defects such as fluctuations in focal spots or a decrease in vacuum degree in the field emission X-ray source device have.

1 schematically shows a configuration of a field emission X-ray source device according to an embodiment of the present invention.
FIG. 2 shows an X-ray target coupled to the anode electrode in the embodiment of FIG. 1.
FIG. 3 shows an example of a mechanical coupling structure for coupling the anode electrode and the target member shown in FIG. 2.
4 shows an example of a mechanical coupling structure for coupling the anode electrode and the target member.
5 shows another example of a mechanical coupling structure for coupling the anode electrode and the target member.
6 shows another example of a mechanical coupling structure for coupling the anode electrode and the target member.
7 schematically shows an anode-side configuration of a field emission X-ray source device according to an embodiment of the present invention.
8 schematically shows an anode-side configuration of a field emission X-ray source device according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments described below may be modified in various ways, and the scope of the present invention is not limited to the following embodiments. Embodiments of the present invention are provided to clearly convey the technical spirit of the invention to those skilled in the art.

1 schematically shows a configuration of a field emission X-ray source device according to an embodiment of the present invention.

The field emission X-ray source device 100 according to the present embodiment, as shown in the drawing, the vacuum vessel 10 and the cathode of one side of the vacuum vessel 10 (the lower portion of the vacuum vessel 10 in this figure) The electron emission source 41 disposed on the electrode 40 and the other side of the vacuum container 10 (the upper portion of the vacuum container 10 in this drawing) are spaced between the electron emission source 41 and the vacuum. And an anode electrode 20 disposed to face each other. The anode electrode 20 is hit by the electron beam E emitted from the electron emission source 41, and a striking unit 31 that provides a target surface inclined with respect to the traveling direction of the electron beam E With a target member 30 having a coupling part 32 formed in one body with the striking part 31 and extending in a direction away from the target surface, and a conductor having higher thermal conductivity than the target member 30 It is made, and includes an anode electrode body mechanically coupled to the coupling portion 32.

The vacuum container 10 may be made of an insulating material such as ceramic, glass or silicon, and may be made of a material such as alumina ceramics. As the vacuum container 10 is made of an insulating material, the field emission X-ray source device 100 is electrically insulated from the anode electrode 20 and the cathode electrode 40. An electron emission source 41 is disposed on the cathode electrode 40, and the electron emission source 41 may be provided on a separate substrate and coupled to the cathode electrode 40, or directly formed on the surface of the cathode electrode 40. It may be. The electron emission source 41 may be, for example, a plurality of nanostructures such as carbon nanotubes. In the case of the electron emission source 41 using carbon nanotubes, a number of carbon nanotubes are directly grown on the surface of the substrate or cathode electrode 40 using chemical vapor deposition (CVD), or a carbon nanotube paste is applied. It can be formed by a method such as firing after.

On the other hand, one side of the vacuum container 10, and more specifically, one side close to the anode electrode 20 has a window that allows X-rays (XB) generated inside the vacuum container 10 to be smoothly discharged to the outside. It may be provided. The window has any of relatively high X-ray transmittance of beryllium (Be), aluminum (Al), magnesium (Mg), aluminum nitride (AlN), aluminum-beryllium alloy (AlBe), silicon oxide (SixOy), titanium (Ti) It may be made of one or an alloy thereof.

A gate electrode 50 may be disposed between the electron emission source 41 and the anode electrode 20. The gate electrode 50 is disposed close to the electron emission source 41 to form an electric field that initiates electron emission. The gate electrode 50 may be provided in the form of a thin metal plate or a metal mesh in which a plurality of holes 51 are formed to allow the electron beam E to pass therethrough. Also, a focusing electrode 60 that forms an electric field for focusing the electron beam E may be disposed between the gate electrode 50 and the anode electrode 20.

The anode electrode 20 forms a high potential difference ranging from tens to hundreds of kV with the cathode electrode 40 on which the electron emission source 41 is disposed, and functions as an accelerating electrode while being discharged from the electron emission source 41 It also serves as an X-ray target that emits X-rays by the collision of accelerated electrons. To this end, the anode electrode 20 includes a striking portion 31 having a target surface obliquely inclined with respect to a direction in which the electron beam E proceeds inside the vacuum container 10, and in a direction away from the target surface. It includes a target member 30 having an engaging portion (32) protruding from the striking portion (31). The striking portion 31 and the engaging portion 32 are integrally formed of the same material. The target member 30 may have various shapes, and the anode electrode body forming the rest of the anode electrode 20 except for the target member 30 is concave corresponding to the protruding shape of the coupling part 32. It may have a portion such as a groove. The target member 30 is mechanically coupled such that other materials, such as a brazing filler, do not intervene in direct contact with the anode electrode body. The specific shape and mechanical coupling structure of the striking portion 31 and the engaging portion 32 will be described later with various embodiments.

The target member 30 is a tungsten (W), copper (Cu), molybdenum (Mo), cobalt (Co), chromium (Cr), iron (E) that emits X-rays by the impact of the accelerated electron beam (E). Fe), silver (Ag), tantalum (Ta), or yttrium (Y). The striking portion 31 emits X-rays while being hit by an accelerated electron, and when continuously hit by an electron beam E in the aging process, the focus on the striking portion 31 reaches a high temperature of about 2700 ° C. or higher, The anode electrode 20 as a whole reaches about 1700 ° C. In order to prevent focal spot fluctuation due to deformation even at such a high temperature, for example, the target member 30 may be formed of tungsten (W) having a high melting point of 3440 ° C. On the other hand, according to the present invention, since the target member 30 is coupled to the anode electrode 20 by mechanical bonding without intervention of other materials such as a brazing filler having a relatively low melting point, the degree of vacuum reduction by outgasing is reduced. It can be prevented.

Here, the anode electrode body may be formed of various conductive metal materials. Among the metal materials that can withstand the high temperature of the above-described level, it is advantageous in terms of heat diffusion that the thermal conductivity is higher than that of the target member 30, and the coefficient of thermal expansion in terms of bonding property with the vacuum container 10 and the vacuum container 10. Similar is advantageous. For example, the anode electrode body may be formed of an iron-nickel-cobalt alloy called Kovar.

FIG. 2 shows an X-ray target coupled to the anode electrode in the embodiment of FIG. 1. As illustrated, the striking portion 31 may be disposed on one side of the anode electrode 20 facing the vacuum space to be inclined with respect to the direction in which the electron beam travels.

FIG. 3 shows an example of a mechanical coupling structure for coupling the anode electrode and the target member shown in FIG. 2.

 FIG. 3 (a) shows an example in which the target member 30a is mechanically coupled to the anode electrode body 20a by a threaded structure. The target member 30a has a flat plate-shaped hitting portion 31a and a cylindrical engaging portion 32a protruding from the hitting portion 31a to the opposite side of the surface that is hit by electrons. A male screw is formed on the outer circumferential surface of the cylindrical coupling portion 32a. The anode electrode body 20a is formed with a cylindrical groove 22a in which a female screw is formed so as to be fastened by screwing with the coupling portion 32a, and accommodates the rest except for the target surface of the striking portion 31a. The groove 21a may be formed.

3 (b) shows an example in which the target member 30b is mechanically coupled to the anode electrode body 20b by a protrusion-groove coupling structure. The target member 30b also has a striking portion 31b in the form of a flat plate and a cylindrical engaging portion 32b protruding from the hitting portion 31b to the opposite side of the surface that is hit by electrons. A projection 33b is provided on the outer circumferential surface of the cylindrical coupling portion 32b. The anode electrode body 20b has a cylindrical groove 22b and a cylindrical groove 22b corresponding to the cylindrical coupling portion 32b so as to be fastened by the coupling portion 32b and the protrusion-groove coupling structure. It is formed on the inner circumferential surface of the guide groove (23b) is provided to guide the entry of the projection (33b) and engaged with and engaged with him by rotation of the target member (30b). A groove 21b may be formed in the anode electrode body 20b to receive the rest of the striking portion 31b except for the target surface.

4 shows an example of a mechanical coupling structure for coupling the anode electrode and the target member.

As shown, the anode electrode body 20c and the target member 30c may be coupled by a key coupling structure. As an example of the key coupling structure, on one side of the hitting portion 31c of the target member 30c, an example of the coupling portion described above is provided with a slide projection-type coupling portion 32c having a constant cross-sectional shape in the slide direction, A guide groove 22c corresponding to the shape of the slide protrusion-type coupling portion 32c may be provided on one side of the anode electrode body 20c. Keyholes 33c and 24c which are linearly communicated with each other in a slide-coupled state may be provided in the slide projection-type engaging portion 32c and the guide groove 22c, and a straight key 34c separately provided therein is provided. Can be inserted. Here, although the example in which the target member 30c and the anode electrode body 20c are combined by a slide coupling method and a key is inserted into the coupling structures is shown, the above-described coupling portion is simply inserted into the groove and a common key is provided to them. Mechanical coupling is also possible through a coupling structure that is inserted and fixed.

5 shows another example of a mechanical coupling structure for coupling the anode electrode and the target member.

As shown, the anode electrode body 20d and the target member 30d may be coupled by a bolted structure. As an example of the bolt coupling structure, the coupling portion 32d protruding in the direction of the anode electrode body 20d from one end of the striking portion 31d of the target member 30d and of the anode electrode body 20d Screw holes 33d and 22d communicating with each other are formed in the receiving portion 22d formed in a shape corresponding to the coupling portion 32d on one side, and one bolt 34d has these screw holes 33d and 22d. It may be provided with a coupling structure in the form of fastening to.

6 shows another example of a mechanical coupling structure for coupling the anode electrode and the target member. The target members 30e and 30f may have a cap shape that covers a portion of the anode electrode bodies 20e and 20f inside the vacuum container. The target member in the form of a cap may be formed by a press process or may be formed by cutting.

Figure 6 (a) is an example of such a cap-shaped target member, the periphery of the anode electrode body 20e from the periphery of the striking portion 31e and the striking portion 31e forming an inclined target surface It shows an example in which the target member 30e having the engaging portion 32e extending to surround is inserted into the anode electrode body 20e corresponding to it by welding. Here, the target member 30e and the anode electrode body 20e may be coupled by fusion, where no other material is interposed therebetween, for example, side surfaces of the coupling portion 32e and the anode electrode body 20e. The portions 34e can be joined by laser welding or spot welding.

Figure 6 (b) is another example of the target member in the above-described cap form, the outer periphery of the anode electrode body (20f) from the periphery of the striking portion (31f) and the striking portion (31f) with an inclined target surface It has a coupling portion (32f) of a form extending to surround the, it shows a target member (30f) is formed with a female screw (34f) on the inner peripheral surface of the coupling portion (32f). A male screw 24f corresponding to the female screw 34f is formed on an outer circumferential surface of the anode electrode body 20f, and a screw connection can be made therebetween.

7 schematically shows an anode-side configuration of a field emission X-ray source device according to an embodiment of the present invention. Compared to the field emission X-ray source device 100 according to the above-described embodiment of FIG. 1, the X-ray source device 110 according to this embodiment has a difference in the configuration of the anode electrode 20 side of the vacuum container 10. Here, the differences from the embodiment of FIG. 1 will be mainly described.

In the field emission X-ray source device 110 according to the present embodiment, the anode electrode 20 bonded to the end of the vacuum container 10 on which the anode electrode 20 is installed is coupled to the inside of the vacuum container 10. 10) It includes a heat sink 80 made of a non-conductive material that is not exposed to the outside. Here, as described above, the anode electrode 20 may include a target member 30 composed of a striking portion 31 and a coupling portion 32.

The non-conductive material heat sink 80 is formed of a material having electrical insulation. A high voltage of tens to hundreds of kV may be applied to the anode electrode 20 through the high voltage cable 90 and the connector 91 at the front end thereof. To this end, a through hole 89 is provided in the heat sink 80 of the non-conductive material, and a connector connection portion 29 may also be provided in the anode electrode 20. By preventing the high voltage anode electrode 20 from being exposed to the outside of the vacuum container 10 having electrical insulation and the heat sink 80 of the non-conductive material, the dielectric strength between the anode electrode 20 and other electrodes Can increase.

On the other hand, the heat sink 80 of the non-conductive material is configured to include a base 81 and a plurality of heat radiation fins 82 integrally formed so as to smoothly discharge heat transferred from the anode electrode 20 to the outside. do. The heat dissipation fin 82 serves to rapidly dissipate heat by widening the contact area with the air as in a general heat sink. For smooth heat dissipation, the heat sink 80 of the non-conductive material may be formed of a metal oxide-based ceramic material having a high thermal conductivity among materials having electrical insulation, and for example, may be formed of alumina ceramics. In addition, as in the present embodiment, the non-conductive material heat sink 80 and the vacuum container 10 may be formed of the same material or a material having a similar coefficient of thermal expansion may prevent bonding defects.

The anode electrode 20 and the heat sink 80 made of a non-conductive material may be joined through a mechanical coupling structure, but may be joined through brazing with each other. This is because the junction between the anode electrode 20 and the non-conductive heatsink 80 has a problem that melting or outgassing of the brazing filler does not occur even when the temperature is significantly lower than that of the target member 30 even during aging. .

8 schematically shows an anode-side configuration of a field emission X-ray source device according to an embodiment of the present invention.

In the field emission X-ray source device 120 according to the present embodiment, the non-conductive material heat sink 80a uses a metal block 83 disposed inside the base 81 and between the anode electrode 20. It includes more. The metal block 83 is also disposed not to be exposed to the outside. At this time, the high voltage cable 90 and the connector 91 at the front end thereof are connected to the connector of the anode electrode 20 through through holes 89 and 839 through the base 81 of the heat sink and the metal block 83, respectively. (29).

The metal block 83 may be formed of a metal material having a higher thermal conductivity than the material forming the base 81 and the heat radiation fin 82 of the non-conductive heat sink 80a. For example, when the anode electrode 20 is formed of kovar or copper (Cu), and the base 81 and the heat radiation fin 82 are formed of alumina ceramics, the metal block 83 is made of aluminum (Al). It can be formed as. The coupling between the metal block 83 and adjacent members may be achieved through brazing or mechanical bonding.

10: vacuum container
20: anode electrode 20a ~ 20f: anode electrode body
30, 30a ~ 30f: target member 31, 31a ~ 31f: striking part
32, 32a to 32f: coupling portion 40: cathode electrode
41: electron emission source 50: gate electrode
60: focusing electrode 80: heat sink
81: base 82: heat sink fins

Claims (8)

Tube-shaped insulated container;
An insulating heat sink covering one side of the insulating container, the first surface facing the insulating container, and the second surface exposed to the outside of the insulating container;
A metal block provided in the insulating container and in close contact with the first surface of the heat sink;
An anode electrode provided in the insulating container and in close contact with the metal block;
A cathode electrode covering the other side of the insulating container and facing the anode electrode;
An electron emission source provided on the cathode electrode and emitting an electron beam toward the anode electrode; And
A target member provided on the anode electrode facing the electron emission source and including a target member generating X-rays by collision of the electron beam,
Field emission X-ray source device. According to claim 1,
Further comprising a connector for applying a voltage to the anode electrode through the heat sink and the metal block from the outside of the insulated container is connected to the anode electrode,
Field emission X-ray source device. According to claim 1,
The target member and the anode electrode has a mechanical coupling structure,
Field emission X-ray source device. The method of claim 3,
The mechanical coupling structure is at least one of a screw coupling structure, a protrusion-groove coupling structure, a key coupling structure, and an interference fitting structure,
Field emission X-ray source device. According to claim 1,
The heat sink,
A base constituting the first surface,
Including a heat radiation fin formed on the second surface,
Field emission X-ray source device. The method of claim 5,
The base and heat sink fins are made of alumina ceramics,
Field emission X-ray source device. delete delete

Images