Electron gun, X-ray generating tube, X-ray generator, and X-ray imaging system

Abstract

This provides a highly reliable X-ray generating tube with high stability in the size and shape of the focal point. [Solution] An X-ray generating tube is provided with an electron gun having an electron emission section, a plurality of grid electrodes, and an insulating support member that supports the plurality of grid electrodes, wherein the electron gun has a conductive section that shields the insulating support member from being directly viewed by electrons emitted from the electron emission section and passing through the grid electrodes.

Description

[Technical Field]

[0001] The present invention relates to an X-ray generator applicable to non-destructive X-ray imaging in the fields of medical devices and industrial equipment, and to an X-ray imaging system equipped with the X-ray generator. [Background technology]

[0002] In recent years, with the miniaturization and multi-layering of semiconductor devices, X-ray inspection equipment equipped with X-ray generating tubes is being used in the inspection of electronic devices such as semiconductor integrated circuit substrates in the industrial field.

[0003] As an electron source for irradiating a target with an electron beam, an X-ray generating tube equipped with an electron gun that protrudes toward the target along the tube's axis is known.

[0004] Patent Document 1 discloses that by providing an electron gun equipped with multiple grid electrodes on the target side, the positional accuracy of the focal point formed on the target and microfocusing can be achieved.

[0005] Furthermore, the multiple grid electrodes in such an electron gun are each supported by an insulating material, thereby defining the distance between the electrodes and ensuring that a predetermined potential is applied to each electrode.

[0006] Patent Document 2 discloses an X-ray generating tube equipped with an electron gun in which multiple grid electrodes are supported at intervals on an insulating support column extending in the axial direction of the tube, with the intention of miniaturizing the focus. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2002-298772 [Patent Document 2] Japanese Patent Publication No. 2007-66694 [Overview of the project] [Problems that the invention aims to solve]

[0008] In an X-ray imaging system using an X-ray generating tube equipped with an electron gun containing grid electrodes where multiple grid electrodes are supported by insulating material, a degradation in the quality of the acquired images sometimes occurred.

[0009] Through the inventor's research, it was found that fluctuations in the focal position or focal shape that occur with the operation history of the X-ray generating tube are related to the deterioration of imaging quality.

[0010] The present invention aims to provide a highly reliable X-ray generating tube and X-ray generating device equipped with an electron gun having a grid electrode supported by an insulating member, thereby suppressing fluctuations in the position or shape of the focal point. Furthermore, the present invention aims to provide an X-ray imaging system that enables high-resolution X-ray imaging by incorporating the X-ray generating device according to the present invention. [Means for solving the problem]

[0011] The first X-ray generating tube according to the present invention comprises a target that generates X-rays by electron irradiation, An X-ray generating tube having an electron gun having an electron emission unit that emits electrons, a plurality of grid electrodes that form an electron beam irradiated toward the target, and an insulating support member that electrically insulates and supports at least two of the plurality of grid electrodes, wherein the electron gun has a conductive portion that blocks the insulating support member from being directly viewed by the electrons emitted from the electron emission unit and passing through the grid electrodes.

[0012] The second X-ray generating tube according to the present invention includes a target that generates X-rays by electron irradiation, An X-ray generating tube having an electron emitting portion that emits electrons, a plurality of grid electrodes that form an electron beam irradiated toward the target, and an insulating support member that electrically insulates and supports at least two of the plurality of grid electrodes, wherein the plurality of grid electrodes define an electron passage through which the electrons emitted from the electron emitting portion pass, and the electron gun has a conductive portion that blocks the insulating support member from being directly visible as viewed from the electron passage.

Advantages of the Invention

[0013] According to the present invention, by having a conductive portion that blocks the insulating support member from being directly visible as viewed from the electron passage in the electron gun of the X-ray generating tube, it is possible to provide a highly reliable X-ray generating tube and an X-ray generating apparatus in which fluctuations in the position or shape of the focal point are suppressed.

Brief Description of the Drawings

[0014] [Figure 1] Schematic configuration diagrams (a) to (h) showing an X-ray generating tube according to a first embodiment of the present invention. [Figure 2] Schematic configuration diagrams (a) to (i) showing an X-ray generating tube according to a reference embodiment. [Figure 3] Conceptual diagrams (a) to (f) of an estimated deposition process of scattered metal particles onto an insulating support member according to the problem of the present invention. [Figure 4] Schematic configuration diagrams (a) to (j) showing an X-ray generating tube according to a second embodiment of the present invention. [Figure 5] Schematic configuration diagrams (a) to (h) showing an X-ray generating tube according to a third embodiment of the present invention. [Figure 6] Schematic configuration diagram showing an X-ray generating apparatus according to a fourth embodiment of the present invention. [Figure 7] Schematic configuration diagram showing an X-ray imaging system according to a fifth embodiment of the present invention.

Modes for Carrying Out the Invention

[0015] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The dimensions, materials, shapes, relative arrangements, etc. of the constituent members described in these embodiments are not intended to limit the scope of the present invention. For parts not particularly illustrated or described in this specification, well-known or publicly known techniques in the relevant technical field are applied.

[0016] <X-ray generating tube> FIG. 1 shows an X-ray generating tube 1 according to the first embodiment of the present invention. The X-ray generating tube 1 is a transmission type X-ray generating tube provided with a conductive portion which is a basic feature of the present invention.

[0017] FIGS. 1(a) and (b) are two views showing the basic configuration of the X-ray generating tube 1, and FIG. 1(b) is a front view of the X-ray generating tube 1 in FIG. 1(a) as seen from the anode side. Further, FIG. 1(c) is a partially enlarged view of FIG. 1(b) showing the focal point formed on the target when the X-ray generating tube 1 of the present embodiment is driven. FIG. 1(d) is an enlarged cross-sectional view of the electron gun 4b of the X-ray generating tube 1 shown in FIG. 1(a). Furthermore, FIGS. 1(e) to (h) are cross-sectional views showing the cross-sections of the electron gun 4b in the virtual planes A-A, B-B, C-C, and D-D shown in FIG. 1(d).

[0018] In the present embodiment, X-rays are generated from the target 5b by irradiating the target layer 5c with an electron beam emitted from the electron emission portion 40. For this reason, the target layer 5c is disposed on the surface of the support substrate 5d facing the electron gun 4b. That is, the electron emission portion 40 is disposed on the cathode 4 so as to face the target 5b. The electrons emitted from the electron emission portion 40 are accelerated by the acceleration electric field formed between the cathode 4 and the anode 5 by the tube voltage applied to the X-ray generating tube 1 to the incident energy necessary for generating X-rays in the target layer 5c.

[0019] The anode 5 includes a target 5b and an anode member 5a connected to the target 5b, and functions as an electrode that defines the anode potential of the X-ray generating tube 1.

[0020] The anode member 5a is made of a conductive material and is electrically connected to the target layer 5c. As shown in Figure 1, the anode member 5a is connected around the support substrate 5d and holds the target 5b.

[0021] Furthermore, the target layer 5c contains target metals such as tantalum, molybdenum, and tungsten, which are metallic elements with high atomic number, high melting point, and high specific gravity. On the other hand, the support substrate 5d is preferably made of a material with high X-ray transparency and high thermal conductivity, such as diamond, silicon nitride, silicon carbide, aluminum nitride, graphite, and beryllium. In particular, diamond is preferred as a support substrate material for a transmission-type target because it has high thermal conductivity derived from sp3 bonds and high transparency to radiation.

[0022] The inside of the X-ray generating tube 1 is under vacuum to ensure the mean free path of the electron beam. The vacuum level inside the X-ray generating tube 1 is 1 × 10⁻⁶. -4 Preferably, the Pa is less than or equal to 1 × 10⁻¹⁰ Pa, and from the viewpoint of stabilizing the electron emission characteristics of the electron emission section 40, -6 It is even more preferable that the pressure be less than or equal to Pa. In this embodiment, the electron emission section 40 and the target layer 5c are located in the internal space or on the inner surface of the X-ray generating tube 1, respectively.

[0023] The vacuum inside the X-ray generating tube 1 is formed by evacuating the tube using an exhaust pipe and vacuum pump (not shown), and then sealing the exhaust pipe. A getter (not shown) may also be placed inside the X-ray generating tube 1 to maintain the vacuum level.

[0024] In the X-ray generating tube 1, an insulating tube 2 is sandwiched between the anode member 5a and the cathode member 4a for the purpose of providing electrical insulation between the electron emission section 40, which is defined by the cathode potential, and the target layer 5c, which is defined by the anode potential. Specifically, one end of the insulating tube 2 is connected to the anode member 5a and the cathode member 4a, respectively, in the axial direction of the tube.

[0025] The insulating tube 2 is made of an insulating material such as glass or ceramic material. The insulating tube 2 made of ceramic is protected on its outer surface with a glass layer 0.1 μm to 100 μm thick to ensure strength.

[0026] In this embodiment, the insulating tube 2, the cathode 4 equipped with an electron emission section 40, and the anode 5 equipped with a target 5b constitute an enclosure that is airtight to maintain a vacuum and robust enough to withstand atmospheric pressure. Therefore, the cathode 4 and anode 5 are connected to both ends of the insulating tube 2 in the axial direction, respectively, thereby constituting the enclosure. Similarly, the support substrate 5d can be said to constitute the enclosure, while also acting as a transmission window that takes out the X-rays generated in the target layer 5c to the outside of the X-ray generating tube 1.

[0027] <Electronic gun> Next, the electron gun, which is a feature of the X-ray generating tube of the present invention, will be explained using Figures 1(a), (d), (e) to (h).

[0028] The cathode 4 comprises an electron gun 4b and a cathode member 4a, which include an electron emission unit 40, a grid electrode 42, and an insulating support member 41 that supports the grid electrode, and the target 5b and the electron emission unit 40 are arranged to face each other.

[0029] The electron emission section 40 can be a hot cathode electron source such as a tungsten filament, an impregnated cathode, or an oxide cathode, or a cold cathode electron source such as a spindt-type cathode made of molybdenum.

[0030] As shown in Figure 1(a), the electron gun 4b of this embodiment protrudes from the cathode member 4a toward the anode 5. This arrangement, in which the electron gun 4b protrudes toward the anode 5, is intended to ensure focal position accuracy without reducing the dielectric strength. Specifically, by separating the creepage path of the insulating tube 2 connecting the cathode 4 and the anode 5 by more than a predetermined distance, while keeping the distance between the electron gun 4b and the target 5b below a predetermined distance, the electron beam emitted from the electron emission unit 40 is less susceptible to the influence of the electric field in the radial direction of the tube.

[0031] The electron gun 4b has an electron emission section 40 and a grid electrode 42 positioned on the portion that protrudes toward the anode 5, and this portion is referred to as the head section. The portion that supports the head section relative to the cathode member 4a is referred to as the neck section. In this embodiment, as shown in Figures 1(d) to (h), the neck section is equipped with a cathode support section 45 that supports the electron emission section 40, a power supply section 43d that supplies the extraction potential to the extraction grid electrode 43, and a power supply section 44d that supplies the focusing potential to the focusing grid electrode 44.

[0032] As shown in Figures 1(d) to (h), the electron gun 4b comprises a lead grid electrode 43 and a focusing grid electrode 44, each having electron passage holes 43f and 44f, and an insulating support member 41 that supports the grid electrode 43 and the focusing grid electrode 44. The electron passage holes 43f and 44f of the grid electrode 43 and the focusing grid electrode 44 define an electron path 7 in the direction from the electron emission unit 40 toward the target 5b.

[0033] Since both the extraction grid electrode 43 and the focusing grid electrode 44 have in common the function of restricting the motion of electrons passing through the electron passage 7 and defining the beam diameter of the electron beam, they are collectively referred to as the grid electrode 42 in the present invention.

[0034] Furthermore, the extraction grid electrode 43 is provided with the intention of controlling the amount of electrons passing through the electron passage holes 43f after electrons emitted from the electron emission unit 40 has been released over time, and multiple potentials are applied by switching between them from a voltage source (not shown). On the other hand, the focusing grid electrode 44 is provided with the intention of forming a focusing electric field for electrons and defining the size of the focal spot 8 formed on the target 5b, and a focusing grid potential having a predetermined potential difference with respect to the electron emission unit 40 is applied from a voltage source (not shown).

[0035] In this specification, the electron path 7 corresponds to the path taken by electrons emitted from the electron emission unit 40 until they pass through the focusing grid electrode 44.

[0036] The lead grid electrode 43 has an annular portion 43a that extends in the radial and circumferential directions of the tube and is provided with an electron passage hole 43f. The annular portion 43a is supported by four insulating support members 41a to 41d that are arranged at 90-degree intervals around the electron passage 7 at the outer edge of the annular portion 43a.

[0037] The insulating support members 41a to 41d are matched in their coefficient of linear expansion with that of the grid electrode 42 in order to alleviate thermal stress at the connection point with the grid electrode 42. The grid electrode 42 is made of molybdenum (α = 4.8 × 10 at 300K). -6 K -1 If it is composed of alumina (α = 7.0 × 10 at 300K) -6 K -1 The following applies. The grid electrode 42 and the insulating support members 41a to 41d are joined via a brazing material (not shown).

[0038] Furthermore, embodiments of the present invention (not shown) also include configurations in which multiple grid electrodes 43 and multiple focusing grid electrodes 44 are arranged. Accordingly, configurations in which there are three or more grid electrodes 42 also include embodiments of the present invention (not shown). In such embodiments, the insulating support member 41 electrically insulates and supports at least two of the multiple grid electrodes 42.

[0039] Furthermore, as shown in Figures 1(d) and (h), the focusing grid electrode 44 is provided with an annular portion 44a that extends in the radial and circumferential directions of the tube, and has electron passage holes 44f through which electrons that have passed through the electron passage holes 43f of the extraction grid electrode 43 can pass.

[0040] Furthermore, the annular sections 43a and 44a do not need to be parallel to the radial direction of the tube (yz plane), and only need to be in a shape that forms an electric field sufficient to define the electron passage 7, and may be cone-shaped. In addition, the annular sections 43a and 44a may be discontinuous shapes such as a mesh grid, a spiral grid electrode, or multiple annular electrodes.

[0041] <First Embodiment> Next, the X-ray generating tube according to the first embodiment, which is equipped with a conductive part that is a feature of the present invention, will be described in more detail with reference to Figures 1(a) to (h).

[0042] The grid electrode 42 of this embodiment includes a drawout grid electrode 43 on the side closer to the electron emission section 40 and a focusing grid electrode 44 on the side further away from the electron emission section 40. The drawout grid electrode 43 further includes tubular portions 43b and 43c that extend in the direction of the tube axis. It can also be said that the tubular portions 43b and 43c extend in a direction intersecting the direction of the tube diameter. The tubular portions 43b and 43c are tubular protrusions that project from the annular portion 43a, on the side of the electron emission section 40 and the side of the focusing grid electrode 44, respectively. The tubular portions 43b and 43c are parts of the drawout grid electrode 43 and, together with the annular portion 43a, are electrically connected to a voltage source (not shown) and have their potential defined.

[0043] Furthermore, the focusing grid electrode 44 is supported at the outer edge of the annular portion 44a by four insulating support members 41a to 41d arranged around the electron passage 7 at 90-degree intervals. The annular portion 44a is positioned to face the target 5b.

[0044] Furthermore, the annular portion 44a is sufficient to form an electric field that defines the electron passage 7, similar to the annular portion 43a, and may be in the form of a mortar-shaped (cone-shaped) or mesh-shaped structure.

[0045] The focusing grid electrode 44 of this embodiment further includes tubular portions 44b and 44c that extend in the direction of the tube axis. It can also be said that the tubular portions 44b and 44c extend in a direction intersecting the direction of the tube diameter. The tubular portions 44b and 44c are tubular protrusions that project toward the electron emission portion 40 and the adjacent anode 5, respectively. The tubular portions 44b and 44c are parts of the focusing grid electrode 44 and, together with the annular portion 44a, are electrically connected to a voltage source (not shown) and have their potential defined.

[0046] As shown in Figures 1(d) and (e), the tubular portion 43b protrudes toward the cathode member 4b so that the insulating support member 41 is not directly visible from the electron passage 7. Here, the tubular portion 43b is spaced apart from the electron emission portion 40 in the radial direction of the tube so that the lead grid electrode 43 and the electron emission portion 40 do not short-circuit.

[0047] Furthermore, as shown in Figures 1(d) and (g), the tubular portions 43c and 44b are positioned to overlap in the axial direction of the tube and protrude in opposite directions from each other, so that the insulating support member 41 is not directly visible from the electron passage 7. In other words, the annular portion 44a and the annular portion 43a, and the tubular portion 43c and the tubular portion 44b are spaced apart from each other so that the grid electrodes 42 (43, 44) do not short-circuit.

[0048] Furthermore, the extraction grid electrode 43 and the focusing grid electrode 44 can be described as a pair of grid electrodes 42 having annular portions 43a and 44a facing each other in the direction of the tube axis, and tubular portions 43c and 44b facing each other in the direction of the tube diameter, as shown in Figures 1(d) and (g). By providing such annular portions 43a and 44a (conductive portions 6), the electron gun 4b of this embodiment suppresses the accumulation of scattered metal particles moving in the direction of the tube diameter on the insulating support members 41a to 41d.

[0049] Furthermore, the tubular portion 43c is located inward in the radial direction of the tube compared to the tubular portion 44b. In other words, the tubular portion 43c of the extraction grid electrode 43, where the annular portion 43a is located closer to the electron emission portion 40, is located inward in the radial direction of the tube compared to the tubular portion 44b of the focusing grid electrode 44, where the annular portion 44a is located further away from the electron emission portion 40.

[0050] The conductive portion 6 (tubular portions 43b, 43c, 44b) plays a role in suppressing the accumulation of metal particles flying from the electron passage 7 on the insulating support member 41, thereby maintaining the insulating properties of the insulating support member 41. As a result, the electron emission portion 40 and the grid electrodes 42 (43, 44) are stably maintained at their respective predetermined potentials. Therefore, the X-ray generating tube 1 according to this embodiment has high reliability because fluctuations in the size, position, and shape of the focal point 8 due to the operating history are suppressed.

[0051] In this embodiment, the conductive portion 6 (tubular portion 43b, 43c, 44b) is the portion of the grid electrode 42 (43, 44) and is conductive. Therefore, as long as the adjacent electron emission portion 40 and grid electrode 42 (43, 44) do not short-circuit, even if metal particles accumulate on the conductive portion 6 (tubular portion 43b, 43c, 44b), no fluctuation occurs in the electric field regulating effect of the grid electrode.

[0052] In the X-ray generating tube 1 according to this embodiment, the electron gun 4b has conductive parts 6 (tubular parts 43b, 43c, 44b) that block the insulating support member 41 from being directly viewed from the electron passage 7, thereby ensuring the insulating properties of the insulating support member 41. By providing an electron gun 4b having such conductive parts 6 (tubular parts 43b, 43c, 44b), it is possible to provide a highly reliable X-ray generating tube 1 in which fluctuations in the size, position, and shape of the focal point 8 are suppressed.

[0053] In this embodiment, the conductive portion 6 (43b, 43c, 44b) was part of the grid electrode 42 (43, 44), but the present invention also includes configurations in which electrically isolated metal materials are arranged from the grid electrode 42 (43, 44). On the other hand, in order to suppress short circuits between the conductive portion 6 and the grid electrode 42, or between the conductive portion 6 and the electron emission portion 40, in the space where the grid electrode 42 (43, 44) is arranged, it is preferable that the conductive portion 6 is part of the grid electrode 42, as in this embodiment.

[0054] Furthermore, in this embodiment, as shown in Figures 1(e) and (g), the conductive parts 6 (43b, 43c, 44b) are tubular in shape so as to block the insulating support members 41a to 41d from being directly viewed from the electron passage 7, but being tubular is not essential. For example, an embodiment (not shown) in which conductive parts are arranged discretely in the circumferential direction corresponding to each of the insulating support members 41a to 41d which are arranged discretely in the circumferential direction is also included in the present invention.

[0055] The mechanism by which metal particles fly from the electron passage 7 and accumulate on the insulating support members 41a to 41d will be described later.

[0056] <Reference form> The inventors of the present invention confirmed the variation in focal diameter associated with the driving history of an X-ray generating tube having an electron gun equipped with a grid electrode supported by an insulating support member.

[0057] Figures 2(a) to 2(e) illustrate an X-ray generating tube 301 according to a reference embodiment that differs from the first embodiment in that the grid electrodes 42 and 43 do not have a tubular portion (conductive portion).

[0058] Figures 2(a) to 2(h) are shown corresponding to Figures 1(a) to 2(h) of the first embodiment. On the other hand, Figure 2(i) is 10 4 This diagram schematically shows the focal spot 308 observed in the X-ray generating tube 304 after one exposure operation, and unlike the first embodiment, an enlargement of the focal spot diameter can be seen.

[0059] As a result of diligent research by the inventors of this application, the following five observational facts regarding the variation in focal diameter associated with the driving history were confirmed in an X-ray generating tube having an electron gun equipped with a grid electrode supported by an insulating support member. • The change in focal diameter did not recover during the rest period and was irreversible. • The square of the correlation coefficient R with respect to the variation in focal diameter 2 The order was tube voltage < exposure intensity ≈ electron beam irradiation dose < filament current of electron emission source. · When analyzing the electron gun of the X-ray tube with a large amount of variation, a decrease in the inter-node resistance between the grid electrodes and between the grid electrode and the electron gun was observed. · When analyzing the electron gun of the X-ray tube with a large amount of variation, an increase in a specific metal was observed in the surface composition of the insulating support member. · The metal with an increase was dominated by the component Ba derived from the electron emission part.

[0060] Based on such observed facts, the inventor of the present application has come to presume that "the factor causing the variation in the focal diameter lies in the deposition of scattered metal particles on the insulating support member 341 accompanying the operation of the X-ray tube."

[0061] <Elementary process of scattered metal particle generation> Next, using FIGS. 3(a) to (f), the elementary process deliberated by the inventor of the present application regarding the generation of scattered metal particles related to the problems of the present invention and the deposition on the insulating support member will be explained.

[0062] Inside the X-ray tube 301, metal particles are floating together with the inevitably remaining gas. Such metal particles are considered to be components partly released into the vacuum space from the electron emission part 340 and the constituent materials of the target layer 305c. From the observation results based on the exposure operation of the X-ray tube and the electron emission operation of the electron gun, as shown in FIG. 3(a), evaporation from the electron emission part 340, sputtering on the target layer 305c and the grid electrode 342, etc. are considered for the release process of the metal particles.

[0063] Since the floating metal particles have a kinetic energy of about several eV or less, most of them are captured at or near the generation location, but the remaining part is ionized by receiving irradiation of electrons and X-rays as shown in FIGS. 3(b) and (c).

[0064] Taking the impregnated electron emission part 340 impregnated with barium oxide as an example, the ionization process of Ba particles evaporated from the electron emission part 340 is shown in [Chemical formula 1] and [Chemical formula 2]. Ba (X-ray incident) → Ba + + e ― [Chemical formula 1] Ba (+e - incident) → Ba + + 2e ― [C2]

[0065] On the other hand, the generated metal ions move towards the cathode member 304 due to the electrostatic force they receive from the electric field inside the electron gun 304b or the X-ray generating tube 301, as shown in Figure 3(d), and most of them are captured by the cathode 304. The captured metal ions are thought to transfer electrons on the cathode 304 and deposit as a metal layer, as shown in [Chemical Formula 3]. Ba + + e - → Ba [Chemistry 3]

[0066] Furthermore, the metal deposited on the cathode 304 is permissible because it does not affect the electric field specified performance of the cathode member 304a and the electron emission section 340 that constitute the cathode 304.

[0067] On the other hand, the remaining metal ions, before being captured by the cathode 304, recombine with scattered electrons and the electron beam, as shown in Figure 3(e), and receive some of the kinetic energy of the electron beam and scattered electrons to become neutral scattered metal particles.

[0068] Because these scattered metal particles are unaffected by the electric field, they can move in the radial direction (yz plane) of the tube, and as shown in Figure 3(f), the metal particles become fixed to the surface of the insulating support member 341, depositing a metal layer. As a result, in the X-ray generating tube 301 which has an electron emission section 304b that does not have a conductive section 6 (tubular section), the electric field regulating performance of the grid electrodes 343 and 344 decreases with the operating history. As a result, it is thought that a change in the focal size from the initial focal spot 8 shown in Figure 2(c) to the defocused focal spot 308 shown in Figure 2(i) is observed with respect to the operating history of the X-ray generating tube 301.

[0069] <Second Embodiment> Figure 4 shows the X-ray generating tube 1 according to the second embodiment. Figures 4(a) to 4(h) are presented in the same manner as Figures 1(a) to 4(h). This embodiment differs from the first embodiment in that, as shown in Figures 4(d) and 4(e) to 4(h), it is provided with an outer tubular portion 44e that conceals the insulating support members 41a to 41d when viewed from the outside of the insulating support member 41.

[0070] In this embodiment, the outer tubular portion 44e also serves as the power supply portion 44d for the focusing grid electrode 44, and can be said to be part of the focusing grid electrode 44 (grid electrode 42).

[0071] The conductive part 6 (tubular parts 43b, 43c, 44b) located inside the electron gun 4b shields the insulating support members 41a to 41d when viewed from the electron passage 7. In contrast, the conductive part 6 (tubular part 44e) located outside the electron gun 4b shields the insulating support members 41a to 41d when viewed from the region sandwiched between the electron gun 4b and the insulating tube 2.

[0072] The technical significance of the outer tubular portion 44e acting as a conductive part will be explained below using Figures 4(a) to 4(j).

[0073] <<Scattered metal particles related to backscattered electrons>> Electrons emitted from the electron emission unit 40 with virtually zero initial velocity pass through the electron path 7, are accelerated by the electrostatic potential of the tube voltage Va, and are incident on the target 5b with kinetic energy Va (eV).

[0074] In target 5b, the energy is converted into thermal energy, secondary electrons, and Auger electrons within the target layer 5c, with the remainder converted into X-rays. The secondary electrons and Auger electrons, which are components that have interacted with the target metal and been slowed down within the target layer 5c, have only kinetic energy of 0-500 (eV) and are emitted behind the target layer 5c, so most of them are re-incident to the anode 5 and captured.

[0075] On the other hand, approximately 20% to 40% of the incident electrons are elastically scattered at the surface of the target layer 5c. The backscattered electrons elastically scattered at the surface of the target layer 5c have a kinetic energy Va (eV) and can reach regions that lie on the equipotential surface of the electron emission section 40.

[0076] In the X-ray generating tube 1, which has an electron gun 4b protruding from the cathode member 4a on the anode 5 side, the electric field between the cathode 4 and anode 5 is deformed by the electron gun 4b on the cathode 4 side, as shown in Figure 4(i).

[0077] The backscattered electrons elastically scattered from the target layer 5c have a scattering angle distribution, and there are components that scatter towards the electron gun 4b as well as components that reach the space between the electron gun 4b and the insulating tube 2.

[0078] Figure 4(i) shows the tube axis directions X0 (y=-Ψ / 2), X1 (y=0), and X2 (y=-Ψ / 4), which have different Y coordinates in the direction of the tube diameter. Figure 4(j) shows the virtual linear potential distribution along the tube axis directions X0 (y=-Ψ / 2), X1 (y=0), and X2 (y=-Ψ / 4). Here, Ψ is the diameter (m) of the anode member 5a.

[0079] Since the electrostatic potential of the electron emission section 40 is cathode potential -Va (eV), backscattered electrons traveling along X2 (y = -Ψ / 4) reach the cathode member 4a side from the electron emission section 40.

[0080] Therefore, backscattered electrons that reach the space between the electron gun 4b and the insulating tube 2 recombine with trace amounts of metal (positive) ions contained in the internal space of the X-ray generating tube 1, transforming into neutral scattered metal particles. In other words, backscattered electrons that reach the space between the electron gun 4b and the insulating tube 2 are thought to generate scattered metal particles in that space, causing metal particles to be deposited on the insulating support member 41.

[0081] The outer tubular portion 44e (conductive portion) of this embodiment suppresses the accumulation of scattered metal particles generated in the space between the electron gun 4b and the insulating tube 2 on the insulating support members 41a to 41d, which would reduce the resistance of the insulating support member 41. As a result, the electron emission portion 40 and the grid electrodes 42 (43, 44) are stably maintained at their respective predetermined potentials. Therefore, as shown in Figure 4(c), the X-ray generating tube 1 according to this embodiment exhibits even greater reliability by suppressing fluctuations in the size, position, and shape of the focal point 8 due to its operating history.

[0082] The outer tubular portion 44e can also be described as a conductive portion provided on the outside of the insulating support members 41a to 41d to suppress the accumulation of scattered metal particles on the insulating support members 41a to 41d from the outside in the radial direction of the pipe.

[0083] The X-ray generating tubes according to the first and second embodiments were shown as examples applied to a transmission type X-ray generating tube equipped with a transmission type target. However, the present invention also includes embodiments of a reflective type X-ray generating tube, which is an X-ray generating tube equipped with an electron gun in which a grid electrode is supported by an insulating support member and is equipped with a reflective type target.

[0084] <Third Embodiment> Figure 5 shows the X-ray generating tube 1 according to the third embodiment. Figures 5(a) to 5(h) are presented in the same manner as Figures 1(a) to 5(h). As shown in Figures 5(d) and 5(g), this embodiment differs from the first and second embodiments in the positional relationship of the annular portions 43c and 44b constituting the conductive portion in the radial direction of the tube. That is, in the radial direction, the annular portions 43c and 44b facing each other are such that the tubular portion 43c of the extraction grid electrode 43 located on the cathode 4 side is located further outward in the radial direction than the tubular portion 44b of the focusing grid electrode 44 located on the anode 5 side. It can also be said that the tubular portion 43c of the extraction grid electrode 43 located on the cathode 4 side is positioned so as not to be directly viewed from the electron passage 7 by the tubular portion 44b of the focusing grid electrode 44 located on the anode 5 side.

[0085] By adopting such an arrangement, the phenomenon that reflected electrons (not shown) backscattered by the annular portion 44a of the focusing grid electrode 44 enter the tubular portion 43c of the extraction grid electrode 43 is suppressed, and the potential fluctuation of the extraction grid electrode 43 is suppressed.

[0086] According to the X-ray generating tube 1 of the present embodiment, not only is the degradation of the insulation properties of the insulating support members 41a to 41d suppressed along with the exposure operation history, but also the influence of reflected electrons incident on the grid electrodes is suppressed. As shown in FIGS. 5(b) and 5(c), it is possible to provide an X-ray generating tube in which the position of the center 8c of the focal spot 8 is more stable and more reliable.

[0087] <X-ray generating device> Next, a configuration example of an X-ray generating device including the X-ray generating tube of the present invention will be described with reference to FIG. 6.

[0088] FIG. 6 shows an X-ray generating device 101 according to the fourth embodiment. The X-ray generating device 101 includes the X-ray generating tube 1 according to the first or second embodiment, a drive circuit 106 for driving the X-ray generating tube 1, and a housing container 107 for housing the X-ray generating device 102 and the drive circuit 106.

[0089] The drive circuit 106 includes a tube voltage circuit 106a that applies a tube voltage between the cathode and the anode, and an electron amount control circuit 106b that controls the electron emission amount of the electron gun 4b. An acceleration electric field is formed between the target layer 5c and the electron emission portion 40 by the tube voltage circuit 106a. By appropriately setting the tube voltage Va corresponding to the layer thickness and metal type of the target layer 5c, the line type required for imaging can be selected.

[0090] The housing container 107 that houses the X-ray generating tube 1 and the drive circuit 106 preferably has sufficient strength as a container and excellent heat dissipation properties, and a metal material such as brass, iron, or stainless steel is used as its constituent material.

[0091] The storage container 107 of the present embodiment is electrically connected to the anode 5 of the X-ray generating tube 1 and is defined at the ground potential.

[0092] On the other hand, an insulating fluid 108 is filled in the extra space in the storage container 107 other than the X-ray generating tube 1 and the drive circuit 106, thereby ensuring electrical insulation between the members stored in the storage container 107 and the storage container 107. The members stored in the storage container 107 include the X-ray generating tube 1, the drive circuit 106, and wirings (not shown) and the like.

[0093] The insulating fluid 108 is a liquid having electrical insulation properties and has a role of maintaining the electrical insulation inside the storage container 107 and a role as a cooling medium for the X-ray generating tube 1. As the insulating fluid 108, electrical insulating oils such as mineral oil, silicone oil, and perfluorinated oil, insulating gases such as SF6, and the like are used.

[0094] The X-ray generating apparatus 101 of the present embodiment includes an electron gun in which stability in the focusing performance of an electron beam is ensured by applying at least the X-ray generating tube 1 according to any one of the first to third embodiments, so that fluctuations of the focal point 8 are suppressed and the reliability is high.

[0095] <X-ray imaging system> Next, a configuration example of an X-ray imaging system including the X-ray generating apparatus of the present invention will be described with reference to FIG. 7.

[0096] FIG. 7 shows an X-ray imaging system 200 according to the fifth embodiment. The X-ray imaging system 200 includes an X-ray detection device 201 that detects X-rays emitted from the X-ray generating apparatus 101 and transmitted through a subject 204, and a system control device 201 that controls the X-ray generating apparatus 101 and the X-ray detection device 201 in cooperation.

[0097] The drive circuit 106 outputs various control signals to the X-ray generating tube 1 under the control of the system control device 202. The emission state of the X-ray beam emitted from the X-ray generating apparatus 101 is controlled by the control signals output by the drive circuit 106.

[0098] The X-ray beam emitted from the X-ray generator 101 passes through the subject 204 and is detected by the detector 206. The detector 206 converts the detected X-rays into an image signal and outputs it to the signal processing unit 205.

[0099] The signal processing unit 205, under the control of the system control unit 202, applies predetermined signal processing to the image signal and outputs the processed image signal to the system control unit 202.

[0100] The system control unit 202 outputs a display signal to the display device 203 for displaying an image based on the processed image signal. The display device 203 displays the image based on the display signal on the screen as an image of the subject 204.

[0101] The X-ray imaging system 200 of this embodiment, by incorporating the X-ray generator 101 according to the fourth embodiment, suppresses fluctuations in the focal point 8 and enables the acquisition of high-quality images with good reproducibility. The X-ray imaging system is applied to non-destructive testing of industrial products and pathological diagnosis of humans and animals. [Explanation of symbols]

[0102] 1 X-ray generating tube 2 Insulating tube 4 cathode 4b Electron gun 5 Anode 5b Target 6 Conductive parts 7 Electron passageway 40 Electron emission part 41 Insulating support member 42 grid electrodes 43 Drawer grid electrodes 44 Focusing grid electrodes

Claims

1. A target that generates X-rays by electron irradiation, An X-ray generating tube having an electron gun having an electron emission section that emits electrons, a plurality of grid electrodes that form an electron beam irradiated toward the target, and an insulating support member that electrically insulates and supports at least two of the plurality of grid electrodes, The electron gun is characterized by having a conductive portion that blocks the insulating support member from being directly viewed by the electrons emitted from the electron emission portion and passing through the grid electrode.

2. The X-ray generating tube according to claim 1, characterized in that the conductive part is potential-defined by a voltage source.

3. The grid electrode is electrically connected to the voltage source, The X-ray generating tube according to claim 2, characterized in that the conductive portion is the portion of the grid electrode.

4. The grid electrode has an annular portion extending in the radial direction of the tube and having an electron passage hole that defines the electron passage path, and a tubular portion connected to the annular portion and extending along the electron passage path. The X-ray generating tube according to claim 1, characterized in that the conductive portion is at least a part of the tubular portion.

5. The X-ray generating tube according to claim 4, characterized in that the grid electrode includes an extraction grid electrode in which the annular portion is arranged to face the electron emission portion and the tubular portion is arranged to overlap the electron emission portion in the axial direction of the tube.

6. The X-ray generating tube according to claim 4 or 5, characterized in that the plurality of grid electrodes include at least one pair of grid electrodes, each having portions where the annular parts of each electrode face each other in the direction of the tube axis and portions where the tubular parts of each electrode face each other in the direction of the tube diameter.

7. The X-ray generating tube according to claim 6, characterized in that, in the pair of grid electrodes, the tubular portion of the grid electrode where the annular portion is located closer to the electron emission portion is located outward in the radial direction of the tube than the tubular portion of the grid electrode where the annular portion is located further away from the electron emission portion.

8. The plurality of grid electrodes include a focusing grid electrode having an annular portion facing the target and defining the size of the focal point formed on the target, The X-ray generating tube according to any one of claims 1 to 7, characterized in that the electron path corresponds to the path taken by the electrons emitted from the electron emission unit until they pass through the focusing grid electrode.

9. The electron gun is configured such that the insulating support member is not directly visible when viewed from the outside in the radial direction of the tube. The X-ray generating tube according to any one of claims 1 to 8, characterized in that the insulating support member has an outer peripheral tubular portion on the outside in the radial direction of the tube, and the conductive portion is the portion of the outer peripheral tubular portion.

10. The X-ray generating tube according to claim 9, characterized in that the outer tubular portion is the portion of the grid electrode.

11. The aforementioned X-ray generating tube is An anode member connected to the target and included in the anode together with the target, A cathode component connected to the electron gun and included in the cathode together with the electron emission source, An X-ray generating tube according to any one of claims 1 to 10, characterized in that it has an insulating tube, one end and the other end in the axial direction of the tube, which are connected to the anode member and the cathode member, respectively.

12. The aforementioned X-ray generating tube is An anode member connected to the target and included in the anode together with the target, A cathode component connected to the electron gun and included in the cathode together with the electron emission source, The device has an insulating tube, with one end and the other end in the axial direction of the tube connected to the anode member and the cathode member, respectively. The X-ray generating tube according to claim 9 or 10, characterized in that the outer tubular portion is fixed to the cathode member.

13. The X-ray generating tube according to any one of claims 1 to 12, characterized in that the conductive portion is located between the electron passage and the insulating support member so as to suppress the accumulation of scattered metal particles moving from the side of the electron passage on the insulating support member.

14. The X-ray generating tube according to any one of claims 1 to 13, characterized in that the target is a transmission type target having a target layer that generates X-rays by electron irradiation and a support substrate that supports the target layer and transmits the X-rays.

15. An X-ray generating apparatus comprising an X-ray generating tube according to any one of claims 1 to 14, and a drive circuit electrically connected to the target and the electron emission unit, respectively, which outputs a tube voltage applied between the target and the electron emission unit.

16. The X-ray generator according to claim 15, An X-ray detection device for detecting X-rays emitted from the aforementioned X-ray generator and transmitted through the subject, A system control device that controls the X-ray generator and the X-ray detection device in coordination, An X-ray imaging system characterized by having the following features.

17. A target that generates X-rays by electron irradiation, An X-ray generating tube having an electron gun having an electron emission section that emits electrons, a plurality of grid electrodes that form an electron beam irradiated toward the target, and an insulating support member that electrically insulates and supports at least two of the plurality of grid electrodes, The plurality of grid electrodes define electron paths through which the electrons emitted from the electron emission unit pass, The electron gun is characterized by having a conductive portion that blocks the insulating support member from being directly viewed from the electron passage.

18. The grid electrode is electrically connected to a voltage source, The X-ray generating tube according to claim 17, characterized in that the conductive portion is the portion of the grid electrode.

19. The grid electrode has an annular portion extending in the radial direction of the tube and having an electron passage hole that defines the electron passage path, and a tubular portion connected to the annular portion and extending along the electron passage path. The X-ray generating tube according to claim 17 or 18, characterized in that the conductive portion is at least a part of the tubular portion.

20. The X-ray generating tube according to claim 19, characterized in that the grid electrode includes an extraction grid electrode in which the annular portion is arranged to face the electron emission portion and the tubular portion is arranged to overlap the electron emission portion in the axial direction of the tube.

21. The X-ray generating tube according to claim 19 or 20, characterized in that the plurality of grid electrodes include at least one pair of grid electrodes, each having portions where the annular parts of each electrode face each other in the direction of the tube axis and portions where the tubular parts of each electrode face each other in the direction of the tube diameter.

22. The X-ray generating tube according to claim 21, characterized in that, in the pair of grid electrodes, the tubular portion of the grid electrode where the annular portion is located closer to the electron emission portion is located further outward in the radial direction than the tubular portion of the grid electrode where the annular portion is located further away from the electron emission portion.

23. The plurality of grid electrodes include a focusing grid electrode having an annular portion facing the target and defining the size of the focal point formed on the target, The X-ray generating tube according to any one of claims 17 to 22, characterized in that the electron path corresponds to the path taken by the electrons emitted from the electron emission unit until they pass through the focusing grid electrode.

24. The electron gun is configured such that the insulating support member is not directly visible when viewed from the outside in the radial direction of the tube. The X-ray generating tube according to any one of claims 17 to 23, characterized in that the insulating support member has an outer peripheral tubular portion on the outside in the radial direction of the tube, and the conductive portion is the portion of the outer peripheral tubular portion.

25. The X-ray generating tube according to claim 24, characterized in that the outer tubular portion is the portion of the grid electrode.

26. The aforementioned X-ray generating tube is An anode member connected to the target and included in the anode together with the target, A cathode component connected to the electron gun and included in the cathode together with the electron emission source, An X-ray generating tube according to any one of claims 17 to 25, characterized in that it has an insulating tube, one end and the other end in the axial direction of the tube, which are connected to the anode member and the cathode member, respectively.

27. The aforementioned X-ray generating tube is An anode member connected to the target and included in the anode together with the target, A cathode component connected to the electron gun and included in the cathode together with the electron emission source, The device has an insulating tube, with one end and the other end in the axial direction of the tube connected to the anode member and the cathode member, respectively. The X-ray generating tube according to claim 24 or 25, characterized in that the outer tubular portion is fixed to the cathode member.

28. The X-ray generating tube according to any one of claims 17 to 27, characterized in that the conductive portion is located between the electron passage and the insulating support member so as to suppress the accumulation of scattered metal particles moving from the electron passage side on the insulating support member.

29. The X-ray generating tube according to any one of claims 17 to 28, characterized in that the target is a transmission type target having a target layer that generates X-rays by electron irradiation and a support substrate that supports the target layer and transmits the X-rays.

30. An X-ray generating apparatus comprising an X-ray generating tube according to any one of claims 17 to 29, and a drive circuit electrically connected to the target and the electron emission unit, respectively, which outputs a tube voltage applied between the target and the electron emission unit.

31. The X-ray generator according to claim 30, An X-ray detection device for detecting X-rays emitted from the aforementioned X-ray generator and transmitted through the subject, A system control device that controls the X-ray generator and the X-ray detection device in coordination, An X-ray imaging system characterized by having the following features.

Images