X-RAY GENERATION APPARATUS AND X-RAY IMAGING APPARATUS

Abstract

X-ray generation apparatus includes: X-ray generation tube having insulating tube with first and second opening ends, cathode closing the first opening end of the insulating tube and having electron emitting portion, and anode closing the second opening end and having target; and accommodating container accommodating the X-ray generation tube. The accommodating container has third opening end, and the X-ray generation tube closes the third opening end. The accommodating container is filled with insulating liquid, first member arranged spaced apart from the second opening end contacts at least part of outer surface of the insulating tube, and the first member is sandwiched between the insulating tube and second member arranged spaced apart from the accommodating container.

Claims

1. An X-ray generation apparatus comprising: an X-ray generation tube including an insulating tube with a first opening end and a second opening end, a cathode arranged to close the first opening end of the insulating tube and including an electron emitting portion, and an anode arranged to close the second opening end and including a target that generates X-rays when electrons from the electron emitting portion collide; and an accommodating container configured to accommodate the X-ray generation tube, wherein the accommodating container has a third opening end, and the X-ray generation tube is arranged to close the third opening end, the accommodating container is filled with an insulating liquid such that the insulating liquid contacts a part of the insulating tube, a first member arranged spaced apart from the second opening end contacts at least a part of an outer surface of the insulating tube, the first member is made of an insulating material, the first member is sandwiched between the insulating tube and a second member arranged spaced apart from the accommodating container, and each of the first member and the second member has a ring-shaped portion.

2. The X-ray generation apparatus according to claim 1, wherein the first member is arranged to cover a contact portion between the cathode and the insulating tube.

3. The X-ray generation apparatus according to claim 1, wherein the outer surface of the insulating tube includes a cylindrical outer side surface, and at least a part of the outer side surface is surrounded by the first member.

4. The X-ray generation apparatus according to claim 1, wherein a space surrounded by the insulating tube is arranged at a location which is inside the accommodating container and outside the X-ray generation tube, the outer surface of the insulating tube includes a surface surrounding the space from outside the space, and the first member is arranged to contact the surface, of the outer surface of the insulating tube, surrounding the space from the outside the space.

5. An X-ray generation apparatus comprising: an X-ray generation tube including an insulating tube with a first opening end and a second opening end, a cathode arranged to close the first opening end of the insulating tube and including an electron emitting portion, and an anode arranged to close the second opening end and including a target that generates X-rays when electrons from the electron emitting portion collide; and an accommodating container configured to accommodate the X-ray generation tube, wherein the accommodating container has a third opening end, and the X-ray generation tube is arranged to close the third opening end, the accommodating container is filled with an insulating liquid such that the insulating liquid contacts a part of the insulating tube, a first member arranged spaced apart from the second opening end contacts at least a part of an outer surface of the insulating tube, the first member is made of an insulating material, the first member is sandwiched between the insulating tube and a second member arranged spaced apart from the accommodating container, a space surrounded by the insulating tube is arranged at a location which is inside the accommodating container and outside the X-ray generation tube, the outer surface of the insulating tube includes a surface surrounding the space from outside the space, and the first member is arranged to contact the surface, of the outer surface of the insulating tube, surrounding the space from the outside the space.

6. The X-ray generation apparatus according to claim 1, wherein the first member is made of fluorine rubber.

7. The X-ray generation apparatus according to claim 1, wherein the second member is made of an insulating material.

8. The X-ray generation apparatus according to claim 1, wherein the second member is made of one of polytetrafluoroethylene, PMMA (polymethyl methacrylate resin), an epoxy resin, polycarbonate, glass, a ceramic, PEEK (polyether ether ketone), ABS (acrylonitrile-butadiene-styrene copolymer synthetic resin), and fluorine rubber.

9. An X-ray generation apparatus comprising: an X-ray generation tube including an insulating tube with a first opening end and a second opening end, a cathode arranged to close the first opening end of the insulating tube and including an electron emitting portion, and an anode arranged to close the second opening end and including a target that generates X-rays when electrons from the electron emitting portion collide; a driving circuit configured to drive the X-ray generation tube; and an accommodating container configured to accommodate the X-ray generation tube, wherein the accommodating container has a third opening end, and the X-ray generation tube is arranged to close the third opening end, the accommodating container is filled with an insulating liquid such that the insulating liquid contacts a part of the insulating tube, a first member arranged spaced apart from the second opening end contacts at least a part of an outer surface of the insulating tube, the first member is made of an insulating material, the first member is sandwiched between the insulating tube and a second member arranged spaced apart from the accommodating container, the accommodating container defines a first space storing the driving circuit, and a second space protruding from the first space, one end of the second space is defined by the third opening, a part or the whole of the insulating tube is contained in the second space, and the outer surface of the insulating tube has a portion that faces a portion of the accommodating container, which defines the second space, without passing through the first member and the second member.

10. The X-ray generation apparatus according to claim 1, wherein the insulating liquid is an insulating oil.

11. The X-ray generation apparatus according to claim 1, wherein the insulating liquid is a fluorine-based inert liquid.

12. The X-ray generation apparatus according to claim 1, wherein the second member is separated from the cathode in an axial direction of the insulating tube.

13. The X-ray generation apparatus according to claim 1, wherein the second member is separated from the anode in an axial direction of the insulating tube.

14. An X-ray imaging apparatus comprising: an X-ray generation apparatus defined in claim 1; and an X-ray detector configured to detect X-rays emitted from the X-ray generation apparatus.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0009] FIG. 1 is a view schematically showing the arrangement of a conventional X-ray generation apparatus for explaining the basic arrangement of an X-ray generation apparatus according to the present disclosure;

[0010] FIG. 2 is a view exemplarily and schematically showing the arrangement of an X-ray generation apparatus according to the first embodiment;

[0011] FIG. 3 is a view exemplarily and schematically showing the arrangement of an X-ray generation apparatus according to the second embodiment;

[0012] FIG. 4 is a view exemplarily and schematically showing the arrangement of an X-ray generation apparatus according to the third embodiment;

[0013] FIG. 5 is a view exemplarily and schematically showing the arrangement of an X-ray generation apparatus according to the fourth embodiment;

[0014] FIG. 6 is a view schematically showing the occurrence of abnormal discharge;

[0015] FIG. 7 is a view exemplifying a triboelectric series in triboelectrification with an insulating liquid;

[0016] FIG. 8 is a view showing a problem in an X-ray generation apparatus according to the fifth embodiment;

[0017] FIG. 9 is a view exemplarily and schematically showing the arrangement of the X-ray generation apparatus according to the fifth embodiment;

[0018] FIG. 10 is a view schematically showing the arrangement of the first modification of the X-ray generation apparatus according to the fifth embodiment;

[0019] FIG. 11 is a view schematically showing the arrangement of the second modification of the X-ray generation apparatus according to the fifth embodiment;

[0020] FIG. 12 is a view schematically showing the arrangement of the third modification of the X-ray generation apparatus according to the fifth embodiment;

[0021] FIG. 13 is a view schematically showing the arrangement of the fourth modification of the X-ray generation apparatus according to the fifth embodiment; and

[0022] FIG. 14 is a block diagram showing the arrangement of an X-ray imaging apparatus according to an embodiment.

DESCRIPTION OF EMBODIMENTS

[0023] Hereinafter, embodiments will be described in detail with reference to the attached drawings. Note, the following embodiments are not intended to limit the scope of the claimed invention. Multiple features are described in the embodiments, but limitation is not made to an invention that requires all such features, and multiple such features may be combined as appropriate. Furthermore, in the attached drawings, the same reference numerals are given to the same or similar configurations, and redundant description thereof is omitted.

[0024] The basic arrangement of an X-ray generation apparatus 100 according to the present disclosure will be described first with reference to FIG. 1. The X-ray generation apparatus 100 can include an X-ray generation tube 1 and an accommodating container 50 that accommodates the X-ray generation tube 1. The X-ray generation apparatus 100 may further include a driving circuit 40 that drives the X-ray generation tube 1, and the driving circuit 40 is accommodated in the accommodating container 50 and can be connected to the X-ray generation tube 1 via a cable 42. A part (an anode 20 to be described later) of the X-ray generation tube 1 can be exposed to the external space of the accommodating container 50 (the external space of the X-ray generation apparatus 100). The internal space of the accommodating container 50 is filled with an insulating liquid 60. From another viewpoint, the internal space of the accommodating container 50 is filled with the insulating liquid 60 except for a space occupied by components (the X-ray generation tube 1, the cable 42, and the like) accommodated in the accommodating container 50. The insulating liquid 60 can be, for example, an insulating oil such as a mineral oil or a chemical synthetic oil. Alternatively, the insulating liquid 60 may be a liquid other than an insulating oil, for example, a fluorine-based inert liquid (for example, Fluorinert).

[0025] The X-ray generation tube 1 can include an insulating tube 10, a cathode 30, and the anode 20. A vacuum is maintained in the internal space of the X-ray generation tube 1. The insulating tube 10 can have a first opening end OP1 and a second opening end OP2. The insulating tube 10 can have a tubular shape such as a cylindrical shape. The insulating tube 10 can be configured to provide vacuum airtightness and insulating properties of the internal space of the insulating tube 10. The insulating tube 10 can be made of, for example, a ceramic material mainly containing alumina or zirconia. Alternatively, the insulating tube 10 can be made of a glass material such as borosilicate glass.

[0026] The cathode 30 can be arranged to close the first opening end OP1 of the insulating tube 10. The cathode 30 includes an electron emitting portion 32. The anode 20 can be arranged to close the second opening end OP2 of the insulating tube 10. The anode 20 can include a target 23 that generates X-rays when electrons from the electron emitting portion 32 collide therewith. The anode 20 can include a target holding plate 22 that holds the target 23, and an electrode 21 that supports the target holding plate 22. The electrode 21 is formed by a conductor, and is electrically connected to the target 23 to apply a potential to the target 23. The anode 20 and the accommodating container 50 can be maintained at, for example, the ground potential but may be maintained at another potential. The target 23 can be made of a material having a high melting point and high generation efficiency of X-rays, such as tungsten, tantalum, or molybdenum. The target holding plate 22 can be made of, for example, a material that can easily transmit X-rays, such as beryllium or diamond.

[0027] The accommodating container 50 can have a third opening end OP3. The accommodating container 50 can include, for example, a first portion 52, a second portion 53, a third portion 54, a fourth portion 55, and a fifth portion 56. The first portion 52 can have a tubular shape such as a cylindrical shape. The first portion 52 can define the third opening end OP3 of the accommodating container 50. In other words, the first portion 52 can include the third opening end OP3. The second portion 53 is formed by a conductor, and is electrically connected to the anode 20 of the X-ray generation tube 1. It may be understood that the second portion 53 forms the anode together with the electrode 21. The second portion 53 can have a ring shape or a frame shape. The second portion 53 can be arranged to contact the insulating liquid 60. Alternatively, a conductive member including the electrode 21 and the second portion 53 can be arranged to contact the insulating liquid 60. The electrode 21 and the second portion 53 may be formed as a single piece of the same material. The fourth portion 55 can have a tubular shape such as a cylindrical shape or a rectangular tubular shape. The third portion 54 is connected to one end of the fourth portion 55, and can have a ring shape or a frame shape. The first portion 52 can be connected to the third portion 54 to project from the third portion 54. The fifth portion 56 can be connected to the other end of the fourth portion 55. Alternatively, the third portion 54, the fourth portion 55, and the fifth portion 56 may be integrated to have a hollow spherical shape, except for the joint portion with the first portion 52.

[0028] The insulating liquid 60 can cause convection in the internal space of the accommodating container 50. The insulating tube 10 has an outer surface 14, an inner surface 15 facing the internal space (vacuum space) of the X-ray generation tube 1, and a contact surfaces 16 that contacts other members (for example, the cathode 30 and the anode 20) forming the internal space (vacuum space) of the X-ray generation tube 1. The outer surface 14 is a surface of the entire surface of the insulating tube 10 excluding the inner surface 15 and the contact surfaces 16. When an entire outer surface 14 of the insulating tube 10 contacts the insulating liquid 60, the insulating tube 10 and the insulating liquid 60 can be charged by friction between the insulating liquid 60 and the outer surface 14 of the insulating tube 10. This charging is called triboelectrification. In general, triboelectrification indicates a phenomenon that friction between two different types of materials causes charges to move between the two types of materials, and thus one material is charged to positive polarity and the other material is charged to negative polarity. The present inventor performed an experiment of measuring the potential of the outer surface of the insulating tube by a surface electrometer after leaving the insulating tube in a convecting insulating oil (insulating liquid). As a result, it was confirmed that the outer surface of the insulating tube was charged to positive polarity and the amount of charge increased in proportion to the time. Charging polarity by friction depends on the characteristics of materials that are rubbed together. Examples of the characteristics of the materials are a triboelectric series and relative permittivity. FIG. 7 shows an example of a triboelectric series with respect to an insulating oil. The triboelectric series indicates positive polarity or negative polarity to which the rubbed material is charged and the ordering of easiness of charging. In the triboelectric series, a material located on the positive polarity side is readily charged to positive polarity and a material located on the negative polarity side is readily charged to negative polarity.

[0029] When the outer surface 14 of the insulating tube 10 is charged to positive polarity, the insulating performance between the cathode 30 and the anode 20 may lower. The insulating performance between the cathode 30 and the anode 20 may depend on a potential difference between the cathode 30 and the anode 20, resistance between the cathode 30 and the anode 20, a distance between the cathode 30 and the anode 20, and the like. As a result of the experiment, it was found that when the insulating tube 10 was charged to positive polarity, the cathode 30 and the anode 20 were short-circuited via the outer surface 14 of the insulating tube 10, as schematically indicated by a thick arrow in FIG. 6. In addition, as a result of the experiment, it was found that when the outer surface 14 of the insulating tube 10, the cathode 30, and the insulating liquid 60 formed a triple point, abnormal discharge readily occurred due to an electron avalanche.

[0030] The X-ray generation apparatus 100 of the present disclosure will exemplarily be described below through a plurality of embodiments shown in FIGS. 2, 3, 4, and 5. Matters not to be mentioned below can comply with the basic arrangement described with reference to FIG. 1.

[0031] FIG. 2 exemplarily and schematically shows the arrangement of an X-ray generation apparatus 100 according to the first embodiment. An accommodating container 50 can be filled with an insulating liquid 60 to contact a part (for example, a second portion 53) of an anode and cover an outer surface 14 of an insulating tube 10 and an outer surface 34 of a cathode 30. In the X-ray generation apparatus 100 of the first embodiment, at least a part of the insulating tube 10 is surrounded by a member 72 so as to reduce abnormal discharge between the cathode 30 and an anode 20 via the insulating tube 10. The member 72 can be made of an insulating material. More specifically, in the X-ray generation apparatus 100 of the first embodiment, the entire region of the outer surface 34 of the insulating tube 10 can be surrounded by the member 72. From another viewpoint, the entire region of the outer surface 14 of the insulating tube 10 can be covered with the member 72. In addition to the entire region of the outer surface 14 of the insulating tube 10, the entire region of the outer surface 34 of the cathode 30 can be covered with the member 72. The first embodiment is effective in avoiding the outer surface 14 of the insulating tube 10, the cathode 30, and the insulating liquid 60 from forming a triple point, thereby making it possible to reduce the occurrence of abnormal discharge.

[0032] To reduce abnormal discharge between the cathode 30 and the anode 20 via the insulating tube 10, the material of the member 72 is decided so that triboelectrification between the member 72 and the insulating liquid 60 causes the member 72 to be charged to negative polarity and the insulating liquid 60 to be charged to positive polarity. In a case where an insulating oil is adopted as the insulating liquid 60, for example, the material of the member 72 can be selected so that triboelectrification between the member 72 and the insulating oil causes the member 72 to be charged to negative polarity in accordance with the triboelectric series exemplified in FIG. 7. As the material of the member 72, for example, polytetrafluoroethylene (Teflon), PMMA (polymethyl methacrylate resin), epoxy, and fluorine rubber (for example, Viton) are preferable. The member 72 is arranged to cover the entire region of the outer surface 14 of the insulating tube 10 and the entire region of the outer surface 34 of the cathode 30, and for example, a mold method, a spray method, a dip method, or the like can thus be applied.

[0033] To reduce abnormal discharge between the cathode 30 and the anode 20 via the insulating tube 10, the material of the member 72 can be decided so that a difference in relative permittivity between the member 72 and the insulating liquid 60 is smaller than a difference in relative permittivity between the member 72 and the insulating tube 10. For example, the member 72 is made of Viton having relative permittivity of 3 or polytetrafluoroethylene having relative permittivity of 2.1, and the insulating tube 10 is made of borosilicate glass having relative permittivity of 4.9 or alumina having relative permittivity of 9. The fact that a difference in relative permittivity between the member 72 and the insulating liquid 60 is smaller than a difference in relative permittivity between the member 72 and the insulating tube 10 may be evaluated at a temperature when generating X-rays or at room temperature (for example, 25 C.). However, there is no large difference between the former case and the latter case.

[0034] A mold method preferable to form the member 72 so as to cover an X-ray generation tube 1 (the outer surface 14 of the insulating tube 10 and the outer surface 34 of the cathode 30) will now be described. The material of the member 72, that is, the covering material is obtained by kneading a principal agent and a curing assistant in advance by a kneading device so as not to contain bubbles, and can be held at a constant temperature to maintain an appropriate flow. In a case of an epoxy-based resin, the temperature is, for example, about 100 C. but the temperature can appropriately be decided in accordance with the material to be used. The covering material can be poured into a container having a size larger than the X-ray generation tube 1 to be covered. At this time, the covering material can be cooled rapidly due to the temperature difference between the container and the covering material, thereby degrading liquidity of the covering material. To prevent this, the container is desirably heated in advance. After the covering material poured into the container is caused to overflow from the container, the covering material can be solidified at an appropriate cooling rate and temperature distribution not to cause a problem such as shrinkage.

[0035] In the X-ray generation tube 1, a high voltage is applied between the anode 20 and the cathode 30. Therefore, if a bubble having a small dielectric constant exists in the member 72 made of the covering material, the electric field is concentrated on the bubble, thereby inducing abnormal discharge. To avoid this, a space where processing of filling the covering material is performed can be exhausted in advance using a vacuum pump to obtain a vacuum degree of about several hundred to several thousand Pa. Furthermore, to improve adhesion between the covering material and the X-ray generation tube 1, the X-ray generation tube 1 may be covered with the member 72 after applying a primer material to the surface of the X-ray generation tube 1 or forming unevenness by blast processing. The thickness of the member 72 is desirably small from a viewpoint of heat dissipation of the X-ray generation tube 1. For example, the thickness of the member 72 is preferably 5 mm or less, and more preferably 3 mm or less. For example, the thickness of the member 72 is preferably 0.3 mm or more, and more preferably 0.5 mm or more.

[0036] FIG. 3 exemplarily and schematically shows the arrangement of an X-ray generation apparatus 100 according to the second embodiment. Matters not mentioned in the second embodiment can comply with the first embodiment or the basic arrangement described with reference to FIG. 1. A member 72 can be arranged to cover a contact portion C between a cathode 30 and an insulating tube 10. Furthermore, the member 72 can be arranged to cover the cathode 30. The second embodiment is also effective in avoiding an outer surface 14 of the insulating tube 10, the cathode 30, and an insulating liquid 60 from forming a triple point, thereby making it possible to reduce the occurrence of abnormal discharge.

[0037] FIG. 4 exemplarily and schematically shows the arrangement of an X-ray generation apparatus 100 according to the third embodiment. Matters not mentioned in the third embodiment can comply with the first or second embodiment or the basic arrangement described with reference to FIG. 1. In the third embodiment, an intermediate layer 75 is provided between a member 72 and an insulating tube 10. The intermediate layer 75 can be made of an insulating material. The intermediate layer 75 can be configured to cover the insulating tube 10. The member 72 can be configured to cover the intermediate layer 75. The intermediate layer 75 can be made of at least one of, for example, Kovar glass, nylon, and a mixture containing a metal oxide that contains silica as a main component. Providing the intermediate layer 75 is advantageous in, for example, forming a smooth surface to cover an outer surface 14 of the insulating tube 10. Forming the intermediate layer 75 is advantageous in suppressing a foreign substance from entering between particles forming the insulating tube 10. As a result, it is possible to improve a creepage withstand voltage on the surface of the member 72 arranged to cover the insulating tube 10. This can prevent abnormal discharge, thereby increasing the life of the X-ray generation apparatus 100.

[0038] FIG. 5 exemplarily and schematically shows the arrangement of an X-ray generation apparatus 100 according to the fourth embodiment. Matters not mentioned in the fourth embodiment can comply with the first to third embodiments or the basic arrangement described with reference to FIG. 1. In the fourth embodiment, a member 72 can include a ring-shaped portion. Alternatively, the member 72 can be a ring-shaped portion. The ring-shaped portion can surround the whole circumference of a part in the axial direction (that is the axial direction of an insulating tube 10 and is also a direction in which an electron beam is emitted from an electron emitting portion 32) of an outer surface 14 of the insulating tube 10. The outer surface 14 of the insulating tube 10 can contact an insulating liquid 60 in a region other than the region surrounded by the member 72. The shortest distance between the member 72 and a cathode 30 is preferably smaller than the shortest distance between the member 72 and an anode 20. The insulating tube 10 may be surrounded by a plurality of members 72 (ring-shaped portions). The plurality of members 72 can be arranged apart from each other with respect to the axial direction of the insulating tube 10. The member 72 can be formed by, for example, Viton. Even if the outer surface 14 of the insulating tube 10 is charged to positive polarity, the amount of charge to positive polarity on the entire outer surface 14 of the insulating tube 10 can be reduced when the member 72 is charged to negative polarity. This can reduce the occurrence of abnormal discharge.

[0039] FIG. 9 exemplarily and schematically shows the arrangement of an X-ray generation apparatus 100 according to the fifth embodiment. Matters not mentioned in the fifth embodiment can comply with the first to fourth embodiments or the basic arrangement described with reference to FIG. 1.

[0040] To improve the insulating performance between an anode 20 and a cathode 30, it is conceivable to increase the creepage distance of an outer surface 14 of an insulating tube 10 between the cathode 30 and the anode 20 by, for example, providing a protrusion portion PP on the insulating tube 10 as shown in FIG. 8, or by increasing the length of the insulating tube 10 in the axial direction. However, in a case where the protrusion portion PP is provided integrally with the insulating tube 10, the shape of the insulating tube 10 becomes complicated. This can increase the manufacturing cost of the insulating tube 10, and decrease yield. On the other hand, when the protrusion portion PP was provided as a separate member, the creepage distance did not increase due to a gap between the insulating tube 10 and the protrusion portion PP. In a case where the length of the insulating tube 10 in the axial direction is increased, the size of the X-ray generation apparatus 100 increases. Hence, a measure for increasing the creepage distance without increasing the size of the X-ray generation apparatus 100 and changing the shape of the insulating tube 10 is demanded.

[0041] In the fifth embodiment, in order to increase the creepage distance between the cathode 30 and the anode 20, a first member 72 arranged spaced apart from a second opening end OP2 of the insulating tube 10 contacts at least a part of the outer surface 14 of the insulating tube 10. The outer surface 14 of the insulating tube 10 has a cylindrical outer side surface (cylindrical surface). In the arrangement example shown in FIG. 9, at least a part of the cylindrical outer side surface (cylindrical surface) of the outer surface 14 of the insulating tube 10 is surrounded by the first member 72 arranged spaced apart from the second opening end OP2 of the insulating tube 10. The first member 72 is sandwiched between the insulating tube 10 and a second member 73 arranged spaced apart from an accommodating container 50.

[0042] The first member 72 may include a ring-shaped portion, like the member 72 in the fourth embodiment, and can be made of fluorine rubber such as Viton. The first member 72 can tightly adhere to the insulating tube 10 by being pressed against the insulating tube 10 by the second member 73. The first member 72 is desirably made of, for example, an elastic material such as a rubber material.

[0043] In the example shown in FIG. 9, the second member 73 is provided around the first member 72. The second member 73 may be a resin-impregnated glass fabric laminated body (for example, a laminated plate or a laminated tube) formed by hot-press molding. The resin-impregnated glass fabric laminated body can be formed by, for example, laminating or winding members (prepregs) prepared by impregnating a glass nonwoven fabric in a resin such as an epoxy resin or a phenol resin and then performing hot-press molding. The second member 73 can be made of, for example, glass epoxy. The second member 73 preferably has an insulating property of 110.sup.5 m or more in a volume resistance at 25 C. For the second member 73, an insulating material such as an epoxy resin, polycarbonate, glass, a ceramic, PEEK (polyether ether ketone), ABS (acrylonitrile-butadiene-styrene copolymer synthetic resin), polytetrafluoroethylene (Teflon), PMMA (polymethyl methacrylate resin), or fluorine rubber (for example, Viton) may be used.

[0044] The second member 73 can have, for example, a ring shape. The second member 73 may be formed from a plurality of dividable portions, or may be formed from a single piece. As in the modification shown in FIG. 10, the second member 73 may also have a function as an insulating container which covers electric components such as a driving circuit 40. Also in the modification shown in FIG. 10, the creepage distance between the cathode 30 and the anode 20 can be increased. The first member 72 and the second member 73 may be provided on the outer surface 14 of the insulating tube 10 and spaced apart from the cathode 30, or may be provided in a contact portion (boundary) between the outer surface 14 of the insulating tube 10 and the cathode 30. According to the latter case, formation of a triple point by the outer surface 14 of the insulating tube 10, the cathode 30, and an insulating liquid 60 can be prevented.

[0045] Furthermore, as in the modification shown in FIG. 11, the first member 72 and the second member 73 may be arranged between the outer surface 14 of the insulating tube 10 and a first portion 52. In the modification shown in FIG. 11, the driving circuit 40 is arranged in a first space SP1 surrounded by a third portion 54, a fourth portion 55, and a fifth portion 56. In addition, in the modification shown in FIG. 11, a second space SP2 surrounded by the first portion 52 and a second portion 53 protrudes from the first space SP1. The first portion 52 may be understood as a portion forming a protrusion portion. In the modification shown in FIG. 11, the first member 72 and the second member 73 are arranged in the second space SP2. The entire insulating tube 10 may be arranged in the second space SP2, or a part of the insulating tube 10 may be arranged in the second space SP2.

[0046] As in the modification shown in FIG. 12, a third member 74 may be provided between the X-ray generation tube 1 and the accommodating container 50 so as to surround a part of the X-ray generation tube 1. This can prevent abnormal discharge between the accommodating container 50 and the X-ray generation tube 1. In this case, the second member 73 and the third member 74 may be integrated together. The third member 74 may also have a function as an insulating container which covers electric components such as the driving circuit 40, like the second member 73 in the modification shown in FIG. 10.

[0047] As in the modification shown in FIG. 13, the cathode 30 can be arranged such that its entirety fits in the second space SP2. An outer surface 34 of the cathode 30 can include a cylindrical side surface 35 and a circular bottom surface 36. In the axial direction of the insulating tube 10 or a direction D in which an electron beam is emitted from an electron emitting portion 32, the cylindrical side surface 35 has a non-zero dimension. The bottom surface 36 of the outer surface 34 of the cathode 30 can face the driving circuit 40. In the radial direction of the insulating tube 10 or a direction orthogonal to the direction D in which an electron beam is emitted from the electron emitting portion 32, the bottom surface 36 has a non-zero dimension. The insulating tube 10 may be arranged to surround the entire side surface 35 of the cathode 30. According to this arrangement, the insulating performance between the cathode 30 and the accommodating container 50 can be improved. In a section (FIG. 13) including the direction D in which an electron beam is emitted (the axis of the X-ray generation tube 1), the second portion 52 or the third portion 54 of the accommodating container 50 can include a convex portion 90 protruding toward the interior of the accommodating container 50.

[0048] Furthermore, the insulating tube 10 may extend to block at least a part of a virtual line VL1 connecting the convex portion 90 and the outer surface 34 of the cathode 30. In this case, a third space SP3 can be partitioned so as to be surrounded by the outer surface 14 of the insulating tube 10 and the bottom surface 36 of the cathode 30. The first member 72 may be arranged in the third space SP3 such that the first member 72 contacts a surface ISS of the outer surface 14 of the insulating tube 10 surrounding the third space SP3. The first member 72 is sandwiched between the insulating tube 10 and the second member 73 arranged spaced apart from the accommodating container 50. The first member 72 can include a ring-shaped portion. This arrangement is effective for increasing the distance between the second member 73 and the first portion 52. In addition, with this arrangement, the second member 73 can block a part of the virtual line VL1. The first member 72 may be arranged to cover the contact portion (boundary) between the cathode 30 and the insulating tube 10.

[0049] In the fifth embodiment exemplified in each of FIGS. 9 to 13, an insulation measure may also be taken between the cathode 30 and the anode 20, as in the first and fourth embodiments.

[0050] FIG. 14 shows the arrangement of an X-ray imaging apparatus 200 according to an embodiment. The X-ray imaging apparatus 200 can include an X-ray generation apparatus 100, and an X-ray detection apparatus 110 that detects X-rays 104 emitted from the X-ray generation apparatus 100 and transmitted through an object 106. The X-ray imaging apparatus 200 may further include a control apparatus 120 and a display apparatus 130. The X-ray detection apparatus 110 can include an X-ray detector 112 and a signal processing unit 114. The control apparatus 120 can control the X-ray generation apparatus 100 and the X-ray detection apparatus 110. The X-ray detector 112 detects or images the X-rays 104 emitted from the X-ray generation apparatus 100 and transmitted through the object 106. The signal processing unit 114 can process a signal output from the X-ray detector 112, and supply the processed signal to the control apparatus 120. The control apparatus 120 displays an image on the display apparatus 130 based on the signal supplied from the signal processing unit 114.

[0051] The present invention is not limited to the above embodiments and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, to apprise the public of the scope of the present invention, the following claims are made.