X-ray tube

Abstract

The X-ray tube of the present invention comprises: an electron gun part, a target for generating X-rays, and a vacuum frame part. The vacuum frame part comprises: a metal frame part for supporting the target; and a valve part which is made of an insulating material and connected to the metal frame part. The electron gun part comprises a focusing electrode part in a cylindrical shape at the end of the electron emission side for focusing the emitted electrons. The electron gun part is supported by the valve part in such a manner that at least a part of the focusing electrode part is located in the metal frame part. When observed from the X-ray generating position of the target, the focusing electrode part blocks the line of sight from the X-ray generating position to the valve part.

Description

Technical Field

[0001] The invention relates to an X-ray tube. Background Art

[0002] Patent Document 1 describes an X-ray tube that generates X-rays. The X-ray tube includes an electron gun that emits electrons, a target that generates X-rays when the electrons are incident thereon, and a valve (a glass airtight container) that contains these and is made of an insulating material. The electron gun is held by the valve.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2007-66694 Summary of the invention

[0006] Problems to be solved by the invention

[0007] Here, in the above-mentioned X-ray tube, the X-rays generated in the target are not only emitted to the outside of the X-ray tube, but also emitted to the vacuum region side of the X-ray tube, and enter the valve portion. At this time, if the X-rays enter the valve portion, which is an insulator, the valve portion may be charged and the withstand voltage capability may be reduced, causing discharge.

[0008] Therefore, an object of the present invention is to provide an X-ray tube capable of suppressing the incidence of X-rays on a valve portion.

[0009] Technical means of solving problems

[0010] An X-ray tube according to one embodiment of the present invention comprises: an electron gun portion that emits electrons; a target that generates X-rays by the incidence of electrons; and a vacuum frame portion that accommodates the electron gun portion and the target, the vacuum frame portion comprising: a metal frame portion that supports the target; and a valve portion that is made of an insulating material and is connected to the metal frame portion, the electron gun portion having a cylindrical focusing electrode portion at the end portion on the electron emission side for focusing the emitted electrons, and is supported by the valve portion in such a manner that at least a portion of the focusing electrode portion is located within the metal frame portion, and when observed from the X-ray generation position of the target, the focusing electrode portion blocks the line of sight from the X-ray generation position to the valve portion.

[0011] In the X-ray tube, the sight line from the X-ray generating position of the target to the valve portion is blocked by the focusing electrode portion, at least a part of which is located in the metal frame portion. Thus, even if the X-rays are emitted from the X-ray generating position of the target toward the vacuum region in the vacuum frame portion, the X-rays from the X-ray generating position toward the valve portion are blocked by the focusing electrode portion. In this way, the X-ray tube can suppress the incidence of X-rays on the valve portion.

[0012] In the X-ray tube, the focusing electrode portion may have a convex portion protruding outward. Thus, the focusing electrode portion can effectively block the line of sight from the X-ray generating position to the valve portion through the convex portion. That is, the focusing electrode portion can effectively block the X-rays from the X-ray generating position toward the valve portion through the convex portion.

[0013] In the X-ray tube, the convex portion may be provided at the end portion on the target side on the outer peripheral surface of the focusing electrode portion. In this case, the convex portion can block the X-rays at a position closer to the X-ray generation position. That is, the convex portion can block the X-rays before the X-rays significantly spread from the X-ray generation position. Thus, the X-ray tube can suppress the protruding height of the convex portion and suppress the incidence of X-rays on the valve portion.

[0014] In the X-ray tube, the corners of the convex portion may be rounded in a curved manner. In this case, the focusing electrode portion can suppress the electric field from concentrating on the corners of the convex portion and suppress the generation of discharge starting from the corners of the convex portion.

[0015] In the X-ray tube, the outer peripheral surface of the focusing electrode portion may be in a tapered shape that becomes larger toward the target. Thus, since the end portion on the target side smoothly becomes larger in diameter, the local electric field concentration on the outer peripheral surface can be suppressed, and the line of sight from the X-ray generation position to the valve portion can be effectively blocked by the portion with the larger diameter. That is, the focusing electrode portion can effectively block the X-rays from the X-ray generation position toward the valve portion by the portion with the larger diameter.

[0016] In the X-ray tube, the corner between the outer peripheral surface of the focusing electrode portion and the end surface of the focusing electrode portion on the target side may be rounded in a curved manner. In this case, the focusing electrode portion can suppress the electric field from concentrating on the corner between the outer peripheral surface of the focusing electrode portion and the end surface of the focusing electrode portion on the target side, and can suppress the generation of discharge starting from the corner.

[0017] [Effects of the Invention]

[0018] According to the present invention, it is possible to suppress the incidence of X-rays on the valve portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a longitudinal sectional view showing the X-ray generating device according to the embodiment.

[0020] Figure 2 Cut along the longitudinal direction Figure 1 End view of an X-ray tube.

[0021] Figure 3 This is an end view of the X-ray tube according to the first modification example cut along the longitudinal direction.

[0022] Figure 4This is a modification of the second grid electrode of the X-ray tube of the first modification, and is an end view of the second grid electrode cut along the longitudinal direction.

[0023] Figure 5 This is an end view of the X-ray tube according to the second modification example cut along the longitudinal direction.

[0024] Figure 6 This is an end view of the X-ray tube according to the third modified example cut along the longitudinal direction.

[0025] Figure 7 This is an end view of the X-ray tube according to the fourth modified example cut along the longitudinal direction. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same or corresponding elements are denoted by the same reference numerals, and duplicate descriptions are omitted.

[0027] like Figure 1 and Figure 2 As shown, the X-ray generator 1 is a microfocus X-ray source used in X-ray nondestructive inspection for observing the internal structure of a subject. The X-ray generator 1 includes an X-ray tube 10 , a device housing 20 , and a power supply 30 .

[0028] The X-ray tube 10 includes a vacuum housing 100, an electron gun 110, and a target T. The electron gun 110 emits an electron beam M (electrons) along an emission axis MX. The X-ray tube 10 is a transmission type X-ray tube that emits X-rays XR generated by the electron beam M from the electron gun 110 incident on the target T and transmitted through the target T itself from an X-ray emission window 104. The X-ray tube 10 is a vacuum sealed type X-ray tube including a vacuum housing 100 having an inner space R having a vacuum. In addition, for convenience of explanation, the side of the electron gun 110 on which the target T is provided is referred to as the "front side", and the opposite side is referred to as the "rear side".

[0029] The vacuum frame portion 100 accommodates the electron gun portion 110 and the target T. The vacuum frame portion 100 has a substantially cylindrical shape extending along the tube axis AX of the X-ray tube 10. In addition, in the present embodiment, the tube axis AX is coaxial with the emission axis MX. Since the tube axis AX is coaxial with the emission axis MX, they are also collectively referred to as the axis L below. The vacuum frame portion 100 includes: a head (metal frame portion) 101 formed of a metal material (for example, stainless steel, copper, copper alloy, iron alloy, etc.), and a valve portion 102 formed of an insulating material (for example, glass, ceramic, etc.). The head 101 is arranged on the front side of the valve portion 102. The head 101 and the valve portion 102 are connected to each other by a valve flange 103 composed of a metal material such as Kovar.

[0030] The valve portion 102 is in a cylindrical shape extending along the tube axis AX of the X-ray tube 10. A cylindrical recess 102w is provided at the rear end of the valve portion 102 and is formed by extending along the tube axis AX in a manner of being folded back toward the front side. That is, the valve portion 102 includes an outer cylinder 102a, an inner cylinder 102b disposed in the outer cylinder 102a, and a cylinder connecting portion 102c connecting the rear end of the outer cylinder 102a and the rear end of the inner cylinder 102b. The outer cylinder 102a and the inner cylinder 102b extend along the axis L.

[0031] A stem portion 105 is provided at the opening of the end portion on the front side of the inner tube 102b in a manner to seal the opening. The stem portion 105 includes a valve flange 106, a stem flange 107, and a stem 108. The stem 108 is made of an insulating material (e.g., glass, ceramic, etc.) and is in the shape of a circular plate. The stem flange 107 is made of a conductive material (e.g., Kovar, etc.) and is in the shape of a cylinder. The stem 108 is fixed to the inner side of the stem flange 107. The valve flange 106 is made of a conductive material (e.g., Kovar, etc.) and is in a roughly cylindrical shape. The stem flange 107 is embedded in and fixed to the valve flange 106. The valve flange 106 is connected to the end portion on the front side of the inner tube 102b of the valve portion 102.

[0032] The rod 108 is provided with a rod pin S. The rod pin S extends across the inner region and the outer region of the vacuum housing 100 and penetrates the rod 108. The rod pin S is electrically connected to each component of the electron gun 110 (heater 121, etc.) to supply power to each component of the electron gun 110.

[0033] The rod portion 105 holds the electron gun portion 110 at a specific position in the internal space R. That is, the electron gun portion 110 is supported by the valve portion 102 via the rod portion 105. That is, the creepage distance between the head portion 101 and the electron gun portion 110 is extended by the recessed portion 102w, the withstand voltage characteristic is improved, and the electron gun portion 110 is arranged close to the target T in the internal space R, so that the electron beam M can be easily micro-focused.

[0034] The head 101 is formed of a metal material and corresponds to the anode of the X-ray tube 10 in terms of potential. The head 101 has openings at both ends and is in a substantially cylindrical shape extending along the axis L. The head 101 is connected to a valve portion 102 extending along the axis L at the opening on the rear side (see Figure 2 ).

[0035] An X-ray exit window 104 is fixed to the front side of the head 101 so as to cover the opening 101a on the front side of the head 101. The X-ray exit window 104 is, for example, in the shape of a circular plate. The X-ray exit window 104 is formed of a material having high X-ray transmittance, such as beryllium, aluminum, or diamond.

[0036] The target T is provided on the surface on the inner space R side of the X-ray exit window 104. That is, the target T is supported by the head 101. In the present embodiment, the target T is formed on the surface on the inner space R side of the X-ray exit window 104. The target T generates X-rays by the incidence of the electron beam M (electrons). As the target T, for example, tungsten, molybdenum, copper, etc. are used.

[0037] The electron gun unit 110 emits electrons toward the target T. The electron gun unit 110 includes a heater 121 , a cathode 122 , a first grid electrode 123 , a second grid electrode (focusing electrode unit) 124 , and an electron gun housing 125 .

[0038] The heater 121 is formed of a filament that generates heat when electricity is supplied. The cathode 122 serves as an electron emission source that emits electrons when heated by the heater 121. The first grid electrode 123 controls the amount of electrons emitted from the cathode 122.

[0039] The second grid electrode 124 focuses the electrons passing through the first grid electrode 123 toward the target T. The second grid electrode 124 also functions as an extraction electrode that forms an electric field for extracting electrons constituting the electron beam M. The first grid electrode 123 is arranged between the cathode 122 and the second grid electrode 124. The electron gun frame 125 is made of a conductive material (such as stainless steel) and has a cylindrical shape. The electron gun frame 125 accommodates the heater 121, the cathode 122, and the first grid electrode 123. The front end of the electron gun frame 125 is connected to the second grid electrode 124, and also serves as a feed path for the second grid electrode 124. The rear end of the electron gun frame 125 is connected to the rod 105.

[0040] The device frame 20 includes a barrel member (accommodating portion) 21 and a power supply housing 33 as a part of the power supply unit 30. The barrel member 21 is formed of metal. The barrel member 21 is in a cylindrical shape with openings at both ends thereof, and has an internal space 21c. The barrel member 21 is inserted into the valve portion 102 of the X-ray tube 10 at the opening 21a on one end side thereof. Thus, the barrel member 21 accommodates at least a part of the X-ray tube 10. More specifically, the barrel member 21 accommodates the entirety of the valve portion 102 in the present embodiment.

[0041] The opening 21a of the cylindrical member 21 is sealed by the head 101 of the X-ray generator 1. In the internal space 21c of the cylindrical member 21, insulating oil 22 which is a liquid electrically insulating substance is sealed.

[0042] The power supply unit 30 has a function of supplying power to the X-ray tube 10. The power supply unit 30 has: an insulating block 31 made of a molded solid insulating material, such as epoxy resin as an insulating resin; a booster unit 32 molded in the insulating block 31; and a power supply housing 33 that accommodates them and is in a rectangular box shape. The booster unit 32 adjusts the boost voltage generated by boosting the input voltage introduced from the outside of the X-ray generating device 1 according to various conditions as needed, thereby generating a high voltage. The insulating block 31 seals the booster unit 32 with an insulating material (such as epoxy resin, etc.). The other end side of the barrel member 21 is fixed to the power supply unit 30 (power supply housing 33). As a result, the opening 21b on the other end side of the barrel member 21 is sealed, and the insulating oil 22 is sealed in the internal space 21c of the barrel member 21.

[0043] In addition, the X-ray generating device 1 includes a feeder 40 that electrically connects the voltage booster 32 and the X-ray tube 10. The feeder 40 supplies power (high voltage) from the power supply 30 to the X-ray tube 10. More specifically, one end of the feeder 40 is connected to the voltage booster 32. The other end of the feeder 40 is inserted into the recess 102w of the valve portion 102 of the X-ray tube 10, and is electrically connected to a rod pin S protruding from the vacuum internal space R at the rod portion 105. The feeder 40 has a plurality of wirings for supplying power.

[0044] In the present embodiment, as an example, the target T (anode) is set to the ground potential, and a high voltage of -100 kV is supplied to the X-ray tube 10 (electron gun unit 110) from the power supply unit 30 via the power feeding unit 40. In fact, a voltage adjusted to the high voltage of -100 kV in accordance with the function of each electrode is applied to each electrode of the electron gun unit 110, but in order to facilitate the understanding of the description, the voltage applied to the electron gun unit 110 is assumed to be -100 kV.

[0045] Next, the details of the second grid electrode 124 included in the electron gun unit 110 will be described. Figure 2 As shown, the second grid electrode 124 focuses the electrons emitted from the electron gun unit 110. The second grid electrode 124 is cylindrical and is provided at the end of the electron gun unit 110 on the target T side (the electron emission side). Here, the electron gun unit 110 is supported by the valve unit 102 via the rod unit 105 in such a manner that at least a portion of the second grid electrode 124 is located in the head unit 101. That is, the front end portion (the end portion on the target T side (the electron emission side)) of the electron gun unit 110 is inserted into the head unit 101.

[0046] Here, the target T generates X-rays at the X-ray generation position P. The X-ray generation position P refers to a position where the electron beam M (electrons) emitted from the electron gun unit 110 enters the target T and generates (emitted) X-rays. Since the X-rays generated at the X-ray generation position P are emitted in all directions with the X-ray generation position P as the center, in addition to being emitted from the X-ray emission window 104 through the target T, they are also emitted toward the inner space R side.

[0047] If the X-rays emitted toward the inner space R enter the valve portion 102 as an insulator, the valve portion 102 may be charged and discharged. Therefore, the second gate electrode 124 has a function of suppressing the X-rays emitted toward the inner space R from entering the valve portion 102 in addition to focusing the electrons.

[0048] Specifically, when observing from the X-ray generation position P of the target T, the second grid electrode 124 blocks the line of sight from the X-ray generation position P to the valve portion 102. Blocking the line of sight here means that the valve portion 102 cannot be directly identified (perspective) from the X-ray generation position P due to the existence of the second grid electrode 124. In other words, it means that the straight line connecting the X-ray generation position P and the valve portion 102 is blocked by the second grid electrode 124.

[0049] Here, the sight line from the X-ray generation position P to the valve portion 102 through the inner side of the second cylindrical grid electrode 124 (the space through which the electrons emitted from the cathode 122 pass) is blocked by the first grid electrode 123 and the electron gun frame portion 125. Here, the second grid electrode 124 blocks the sight line from the X-ray generation position P to the valve portion 102 in such a manner that the valve portion 102 cannot be directly identified from the X-ray generation position P through the outer side of the second cylindrical grid electrode 124 (the space between the second grid electrode 124 and the vacuum frame portion 100). More specifically, the second grid electrode 124 blocks the sight line from the X-ray generation position P to the valve portion 102 in such a manner that the valve portion 102 cannot be directly identified from the X-ray generation position P through the gap between the inner peripheral surface of the head portion 101 and the outer peripheral surface of the second grid electrode 124.

[0050] In more detail, the second grid electrode 124 has: a cylindrical portion 124a in a cylindrical shape, and a convex portion 124b. The cylindrical portion 124a extends along the axis L. In the present embodiment, the cylindrical portion 124a is in a cylindrical shape extending linearly along the axis L. The convex portion 124b is provided on the outer peripheral surface of the cylindrical portion 124a. The convex portion 124b protrudes from the outer peripheral surface of the cylindrical portion 124a toward the outside (the inner peripheral surface side of the head 101). That is, the second grid electrode 124 has a convex portion 124b protruding toward the outside. The convex portion 124b is provided at the end of the outer peripheral surface of the cylindrical portion 124a on the target T side.

[0051] In addition, the convex portion 124b extends across the entire circumferential area on the outer peripheral surface of the barrel 124a. That is, the convex portion 124b is in the shape of a ring through which the barrel 124a passes inside. The corners on the outer peripheral side of the convex portion 124b are rounded in a curved manner. In more detail, on the outer peripheral side of the annular convex portion 124b (the side protruding from the barrel 124a), the corner K1 on the front side is rounded in a curved manner. Similarly, on the outer peripheral side of the annular convex portion 124b (the side protruding from the barrel 124a), the corner K2 on the rear side is rounded in a curved manner. The curved R shape (curvature) of the corner K1 and the curved R shape (curvature) of the corner K2 may be different from each other or the same as each other. The shape of the cross section of the convex portion 124b may also be semicircular.

[0052] The second grid electrode 124 blocks the line of sight from the X-ray generation position P toward the valve portion 102. Specifically, for example, as shown by arrow A1, the line of sight from the X-ray generation position P toward the valve portion 102 (outer cylinder 102a) is blocked by the convex portion 124b. In addition, for example, although the line of sight indicated by arrows A2 and A3 is from the X-ray generation position P toward the head 101 and is not blocked by the second grid electrode 124, since the head 101 is made of a metal material, it will not be charged even if X-rays are incident.

[0053] The second grid electrode 124 is made of, for example, a metal material that can shield X-rays. As the material of the second grid electrode 124, for example, tungsten, molybdenum, tantalum, stainless steel, etc. can also be used. In addition, the electron gun unit 110 becomes a high temperature. Therefore, the second grid electrode 124 can also be made of, for example, a high-melting-point metal material having a melting point of a predetermined temperature (for example, 1000 degrees) or more among the metal materials that can shield X-rays. As the high-melting-point metal material, for example, tungsten, molybdenum, tantalum, etc. can also be used.

[0054] In addition, Figure 2 In FIG. 1 , as an example, the shape of the inner peripheral surface of the second grid electrode 124 is a cylindrical shape extending linearly in the direction of the axis L. However, the shape of the inner peripheral surface of the second grid electrode 124 may adopt various shapes.

[0055] As described above, in the X-ray tube 10, the line of sight from the X-ray generation position P of the target T to the valve portion 102 is blocked by the second grid electrode 124. Therefore, even if X-rays are emitted from the X-ray generation position P of the target T toward the internal space R (vacuum region) of the vacuum frame portion 100, the X-rays from the X-ray generation position P toward the valve portion 102 are blocked by the second grid electrode 124. That is, the X-rays that travel straight from the X-ray generation position P toward the valve portion 102 (X-rays that directly enter the valve portion 102 from the X-ray generation position P) are blocked by the second grid electrode 124. Therefore, it is possible to suppress the valve portion 102 from being charged due to the X-rays entering the valve portion 102. In this way, the X-ray tube 10 can suppress the X-rays from entering the valve portion 102.

[0056] In addition, since the front end portion (the end portion on the target T side (electron emission side)) of the second grid electrode 124 is configured to be located inside the head portion 101, it is possible to efficiently block X-rays from the X-ray generation position P toward the valve portion 102, compared with the case where the entire second grid electrode 124 is configured to be located inside the valve portion 102. Assuming that the entire second grid electrode 124 is configured to be located inside the valve portion 102, the X-rays from the X-ray generation position P toward the valve portion 102 have already been greatly extended even near the front end portion of the second grid electrode 124. Therefore, in order to block the X-rays from the X-ray generation position P toward the valve portion 102 by the second grid electrode 124, the second grid electrode 124 must be continuously extended to the vicinity of the inner wall of the valve portion 102. In this case, since the second grid electrode 124 is close to the vacuum frame portion 100, the withstand voltage capability between the two is reduced, and discharge is easily generated. In addition, since the weight of the second grid electrode 124 is greatly increased, the shock resistance of the electron gun portion 110 is also reduced. In contrast, by arranging the front end portion (the end portion on the target T side (electron emission side)) of the second grid electrode 124 to be located inside the head portion 101, it is possible to block X-rays before they significantly spread from the X-ray generation position P. Therefore, it is possible to suppress the portion (e.g., the convex portion 124b) of the second grid electrode 124 that blocks X-rays from becoming larger, and it is possible to suppress a reduction in the withstand voltage capability and shock resistance of the electron gun unit 110.

[0057] The second grid electrode 124 has a convex portion 124b protruding outward from the cylindrical portion 124a. Thus, the second grid electrode 124 can effectively block the line of sight from the X-ray generation position P to the valve portion 102 through the convex portion 124b. That is, the second grid electrode 124 can effectively block the X-rays from the X-ray generation position P toward the valve portion 102 through the convex portion 124b. In this case, the second grid electrode 124 can suppress the overall size of the second grid electrode 124 from increasing, and can effectively block the line of sight toward the valve portion 102 using the convex portion 124b.

[0058] In addition, the second grid electrode 124 has a shape in which the portion other than the convex portion 124b is narrowed. That is, the portion of the barrel portion 124a of the second grid electrode 124 where the convex portion 124b is not provided has a shape that is narrowed relative to the portion provided with the convex portion 124b (a shape with a smaller outer diameter). As a result, the second grid electrode 124 can increase the distance between the inner surface of the head 101 and the outer surface of the second grid electrode 124 in the portion other than the convex portion 124b (the portion where the outer circumferential surface of the barrel portion 124a is exposed). Therefore, the second grid electrode 124 can suppress the generation of discharge between the inner surface of the head 101 and the outer circumferential surface of the second grid electrode 124.

[0059] In addition, since the second grid electrode 124 is narrowed except for the protrusion 124 b , the overall size of the second grid electrode 124 can be reduced, and an increase in the weight of the second grid electrode 124 itself can be suppressed, and a decrease in the vibration resistance of the electron gun unit 110 can be suppressed.

[0060] The convex portion 124b is provided at the end portion of the front side (target T side) of the outer peripheral surface of the cylinder portion 124a. In this case, the convex portion 124b can block X-rays at a position closer to the X-ray generation position P. That is, the convex portion 124b can block X-rays before the X-rays significantly spread from the X-ray generation position P. Thus, the X-ray tube 10 can suppress the protruding height of the convex portion 124b and suppress the incidence of X-rays on the valve portion 102.

[0061] In addition, the shape of the second grid electrode 124 is not limited to the above-mentioned shape. For example, the corners K1 and K2 of the convex portion 124b of the second grid electrode 124 may not be rounded in a curved manner. The convex portion 124b may be provided at the end of the target T side on the outer peripheral surface of the cylinder 124a. That is, the convex portion 124b may be provided at a position offset from the end of the target T side toward the rear side on the outer peripheral surface of the cylinder 124a.

[0062] (First Modification of X-Ray Tube)

[0063] Next, a first modified example of the X-ray tube 10 of the above-mentioned embodiment will be described. The following description will focus on the differences from the X-ray tube 10 of the embodiment, and the description of the common structures will be omitted. In the other modified examples described below, only the differences will be described. Figure 3 As shown, the X-ray tube 10A includes a second grid electrode (focusing electrode portion) 126 having a shape different from that of the second grid electrode 124 , instead of the second grid electrode 124 of the X-ray tube 10 of the embodiment.

[0064] The second grid electrode 126 is in a cylindrical shape. In the present embodiment, the second grid electrode 126 is in a cylindrical shape extending along the axis L. The outer peripheral surface F1 of the second grid electrode 126 is in a tapered shape that becomes larger in diameter as it approaches the target T. In the present modification, the outer peripheral surface F1 of the second grid electrode 126, as an example, is in a tapered shape that gradually (smoothly) becomes larger in diameter at a certain ratio as it approaches the target T. The wall thickness of the second grid electrode 126 becomes thicker as it approaches the target T side (as it approaches the front side).

[0065] In addition, Figure 3 In FIG. 1 , as an example, the shape of the inner peripheral surface of the second grid electrode 126 is a cylindrical shape extending linearly in the direction of the axis L. However, the shape of the inner peripheral surface of the second grid electrode 126 may adopt various shapes.

[0066] The corner K3 between the outer peripheral surface F1 of the second grid electrode 126 and the end surface F2 of the second grid electrode 126 on the target T side (front side) is rounded in a curved manner. Therefore, the second grid electrode 126 is reduced in diameter as the corner K3 is bent as it approaches the target T, after increasing in diameter to a specific position by the tapered shape, and is connected to the end surface F2. In addition, the end surface F2 becomes a flat surface portion as opposed to the target T. That is, since the end surface F2 of the frontmost end portion of the second grid electrode 126 becomes a flat surface portion as opposed to the target T, X-rays can be blocked at a position closer to the X-ray generation position P. That is, since X-rays can be blocked before they significantly expand from the X-ray generation position P, the diameter of the tapered shape can be suppressed from increasing. Therefore, the voltage resistance and shock resistance of the electron gun unit 110 can be suppressed from being reduced. In addition, since the second grid electrode 126 has a thicker wall thickness toward the target T side (toward the front side), it can have sufficient X-ray shielding ability on the target T side (front side) and suppress unnecessary weight increase on the rear side.

[0067] As described above, the end of the target T side of the second grid electrode 126 of the X-ray tube 10A has a large diameter, and the large diameter portion can effectively block the line of sight from the X-ray generation position P to the valve portion 102. That is, the second grid electrode 126 can effectively block the X-rays from the X-ray generation position P to the valve portion 102 by the large diameter portion. In this way, the second grid electrode 126 can suppress the size of the second grid electrode 126 as a whole from increasing, and can effectively block the X-rays toward the valve portion 102. Therefore, the X-ray tube 10A can suppress the X-rays from being incident on the valve portion 102, similarly to the X-ray tube 10 of the embodiment.

[0068] In addition, the second grid electrode 126 has a shape that narrows as it moves away from the target T. That is, the outer diameter of the outer peripheral surface F1 of the second grid electrode 126 becomes smaller as it moves away from the target T. As a result, the second grid electrode 126 can increase the distance between the inner surface of the head 101 and the outer peripheral surface F1 of the second grid electrode 126 in the portion other than the large diameter portion. Therefore, the second grid electrode 126 can suppress the generation of discharge between the inner surface of the head 101 and the outer peripheral surface F1 of the second grid electrode 126.

[0069] In addition, the outer peripheral surface F1 of the second grid electrode 126 is formed into a smooth tapered shape, and a portion (concave portion) that is shaped like an inward (inner peripheral side) is not formed on the outer peripheral surface F1 of the second grid electrode 126. Therefore, in addition to suppressing the electric field from being locally concentrated on the outer peripheral surface F1 and suppressing discharge, it is also possible to suppress dust and the like from being attached to the outer peripheral surface F1 of the second grid electrode 126. For example, the dust and the like can be shavings and the like when the second grid electrode 126 is formed. In this way, since the X-ray tube 10A can suppress the dust and the like from being attached to the outer peripheral surface F1 of the second grid electrode 126, it is possible to suppress the generation of discharge starting from the dust and the like.

[0070] The corner K3 of the second grid electrode 126 is rounded in a curved manner. In this case, the second grid electrode 126 can suppress the concentration of the electric field on the corner K3 and suppress the generation of discharge starting from the corner K3.

[0071] In addition, the shape of the second gate electrode 126 is not limited to the above-mentioned shape. For example, the corner K3 of the second gate electrode 126 may not be rounded in a curved manner.

[0072] (Modification Example of Second Gate Electrode)

[0073] Next, a modification of the second grid electrode 126 of the X-ray tube 10A according to the first modification will be described. Figure 4 As shown, the second grid electrode (focusing electrode portion) 126A is different from the second grid electrode 126 of the first modification example described above mainly in the shape of the inner peripheral surface F3.

[0074] The second grid electrode 126A has a rear wall portion B at the end portion on the rear side (the electron gun frame portion 125 side). The rear wall portion B is provided with an exit hole Ba through which electrons emitted from the cathode 122 pass. On the front side of the rear wall portion B, the shape of the inner peripheral surface F3 of the second grid electrode 126A is a generally tapered shape that becomes larger in diameter toward the target T side. More specifically, the inner peripheral surface F3 of the second grid electrode 126A is composed of the first cylindrical portion N1, the first tapered cylindrical portion N2, the connecting portion N3, the second cylindrical portion N4, the second tapered cylindrical portion N5, and the third cylindrical portion N6 in order from the rear wall portion B side toward the end portion on the target T side.

[0075] The first cylindrical portion N1 extends along the axis L and is in the shape of a cylinder with a larger diameter than the exit hole Ba. The inner diameter of the first cylindrical portion N1 is constant. The first tapered cylindrical portion N2 extends along the axis L and is in the shape of a cone whose diameter gradually increases as it approaches the target T side. The rear end of the first tapered cylindrical portion N2 is connected to the front end of the first cylindrical portion N1. The second cylindrical portion N4 extends along the axis L and is in the shape of a cylinder. The inner diameter of the second cylindrical portion N4 is larger than the inner diameter of the front side of the first tapered cylindrical portion N2. The inner diameter of the second cylindrical portion N4 is constant. The connecting portion N3 is in the shape of a ring that connects the front end of the first tapered cylindrical portion N2 and the rear end of the second cylindrical portion N4.

[0076] The second tapered cylindrical portion N5 extends along the axis L and has a tapered shape that gradually increases in diameter as it approaches the target T side. The end portion on the rear side of the second tapered cylindrical portion N5 is connected to the end portion on the front side of the second cylindrical portion N4. The third cylindrical portion N6 extends along the axis L and has a cylindrical shape. The inner diameter of the third cylindrical portion N6 is the same as the inner diameter on the front side of the second tapered cylindrical portion N5. The end portion on the rear side of the third cylindrical portion N6 is connected to the end portion on the front side of the second tapered cylindrical portion N5.

[0077] As an example, the length of the first cylindrical portion N1 in the direction of the axis L is shorter than the length of the first tapered cylindrical portion N2 in the direction of the axis L. As an example, the length of the first tapered cylindrical portion N2 in the direction of the axis L is shorter than the length of the second cylindrical portion N4 in the direction of the axis L. As an example, the length of the second cylindrical portion N4 in the direction of the axis L is shorter than the length of the second tapered cylindrical portion N5 in the direction of the axis L. As an example, the length of the third cylindrical portion N6 in the direction of the axis L is longer than the length of the first cylindrical portion N1 in the direction of the axis L, and shorter than the length of the first tapered cylindrical portion N2 in the direction of the axis L.

[0078] The corner K4 between the inner peripheral surface F3 (third cylindrical portion N6) of the second grid electrode 126A and the end surface F2 on the target T side (front side) of the second grid electrode 126A is rounded in a curved manner. In this modified example, as an example, the curved R shape (curvature) of the corner K3 becomes gentler (smaller curvature) than the curved R shape (curvature) of the corner K4.

[0079] As described above, the second gate electrode 126A, like the second gate electrode 126 of the first modified example, can suppress the incidence of X-rays on the valve portion 102. In addition, the second gate electrode 126A can provide a smooth outer surface by easing the curved R shape (curvature) of the corner K3 connecting the outer peripheral surface F1 and the end surface F2, and can provide a smooth outer surface, and by providing the shape of the inner peripheral surface F3 as described above, it is possible to achieve both suppression of a decrease in withstand voltage capability and proper focusing of electrons emitted from the cathode 122.

[0080] The shape of the second grid electrode 126A is not limited to the above-mentioned shape. For example, the corners K3 and K4 of the second grid electrode 126 may not be rounded in a curved manner. The shape of the inner peripheral surface F3 of the second grid electrode 126A is not limited to the above-mentioned shape.

[0081] (Second Modification of X-ray Tube)

[0082] Next, a second modified example of the X-ray tube 10 of the above embodiment will be described. Figure 5 As shown, the X-ray tube 10B is a reflection type X-ray tube. The X-ray tube 10B is provided with a target support 109 for supporting a target T at a position in front of an electron gun unit 110. The target T is formed on a target forming surface 109a of the target support 109. The target forming surface 109a is provided on the outer surface of the target support 109 in such a manner that the normal direction of the target forming surface 109a intersects with the axis L direction.

[0083] The head (metal frame) 101B of the X-ray tube 10B has an opening 101a at a position different from the front position of the front side of the electron gun unit 110. The head 101B is formed of a metal material similar to the head 101 of the X-ray tube 10 of the above-mentioned embodiment, and corresponds to the anode of the X-ray tube 10B in terms of potential. The opening 101a of the head 101B is covered by an X-ray exit window 104. The X-ray tube 10B emits X-rays generated by the electron beam M from the electron gun unit 110 incident on the target T from the X-ray exit window 104.

[0084] The second grid electrode 124 blocks the line of sight from the X-ray generating position P toward the valve portion 102. Specifically, as shown by arrow A1, the line of sight from the X-ray generating position P toward the valve portion 102 (outer cylinder 102a) is blocked by the convex portion 124b. In addition, the lines of sight indicated by arrows A2 and A3 are from the X-ray generating position P toward the head 101B and are not blocked by the second grid electrode 124.

[0085] In this case, the X-ray tube 10B is a reflection type X-ray tube. In this case, the X-ray tube 10B can block X-rays from the X-ray generation position P toward the valve portion 102 by the second grid electrode 124 and suppress the incidence of X-rays on the valve portion 102, similarly to the X-ray tube 10 of the embodiment.

[0086] (Third Modification of X-ray Tube)

[0087] Next, a third modified example of the X-ray tube 10 of the above embodiment will be described. Figure 6 As shown, the X-ray tube 10C of this modification is a reflection type X-ray tube similar to the X-ray tube 10C of the second modification. However, the target support 109 supporting the target T of the X-ray tube 10C of this modification is held by the holding valve portion 142 .

[0088] In more detail, the vacuum frame portion 100C includes: a valve portion 102, a frame portion (metal frame portion) 141, and a valve holding portion 142. The frame portion 141 is formed of a metal material (e.g., stainless steel, copper, copper alloy, iron alloy, etc.). The frame portion 141 is cylindrical and is configured to extend along the axis L. An opening 141a is provided in the frame portion 141. The opening 141a is covered by the X-ray exit window 104. The end portion of the rear side of the frame portion 141 is connected to the end portion of the front side of the valve portion 102 through the valve flange 103.

[0089] The valve holding portion 142 is formed of an insulating material (e.g., glass, ceramic, etc.). The valve holding portion 142 is cylindrical and is configured to extend along the tube axis AX (axis L). The rear end of the valve holding portion 142 is connected to the front end of the frame portion 141 through a connecting portion 143 made of a metal material such as Kovar.

[0090] The target support body 109 supporting the target T is arranged in the frame body 141 and the holding valve part 142. The target support body 109 is connected to the front end of the holding valve part 142, and extends from the connection part with the holding valve part 142 toward the electron gun part 110. The holding valve part 142 is connected to the target support body 109 through a connection part 144 made of a metal material such as Kovar. In this way, the frame body 141 supports the target T (target support body 109) through the holding valve part 142. The X-ray tube 10C emits X-rays generated by the electron beam M from the electron gun part 110 incident on the target T from the X-ray exit window 104.

[0091] Here, in the X-ray tube 10C of the present modification, the electron gun section 110 is supported by an insulator (valve section 102), and the target T (target support body 109) is also supported by an insulator (holding valve section 142). Thus, voltages can be applied to each of the electron gun section 110 side and the target T side. That is, for example, when the X-ray tube 10C requires a voltage of 100 kV for X-ray irradiation, the frame section 141 is set to a ground potential, a voltage of -50 kV is applied to the electron gun section 110 side, and a voltage of 50 kV is applied to the target T side. Thus, a required potential difference of 100 kV can be obtained between the target T and the electron gun section 110. In this way, by dividing the required voltage and applying it to the target T side and the electron gun section 110 side, the voltage value itself applied to each part can be reduced, and the withstand voltage capability required for each part can be reduced.

[0092] In the X-ray tube 10C of this modification, the line of sight from the X-ray generation position P toward the valve portion 102 can also be blocked by the second grid electrode 124. Therefore, the X-ray tube 10C can block the X-rays from the X-ray generation position P toward the valve portion 102 by the second grid electrode 124, and can suppress the incidence of the X-rays on the valve portion 102, similarly to the X-ray tube 10 of the embodiment.

[0093] (Fourth Modification of X-ray Tube)

[0094] Next, a fourth modified example of the X-ray tube 10 of the above embodiment will be described. Figure 7 As shown, the X-ray tube 10D is different from the X-ray tube 10 of the above embodiment in that the valve portion 102D is cylindrical. That is, the valve portion 102D is different from the X-ray tube 10 of the above embodiment in that the rear end is not folded back but is in a cylindrical shape extending in a straight line. The X-ray tube 10D includes a vacuum frame portion 100D, an electron gun portion 110, and a target T.

[0095] The vacuum housing 100D accommodates the electron gun 110C and the target T. The vacuum housing 100D includes a head 101 and a valve 102D made of an insulating material (eg, glass, ceramic, etc.). The head 101 and the valve 102D are connected to each other via a valve flange 103 made of Kovar or the like.

[0096] The valve portion 102D is formed into a cylindrical shape extending along the tube axis AX (axis L). The opening at the rear end of the valve portion 102D is provided with a rod portion 105D to seal the opening. The opening at the front end of the valve portion 102D is sealed by the head portion 101 .

[0097] The rod portion 105D holds the electron gun portion 110 at a specific position in the internal space R. That is, the electron gun portion 110 is supported by the valve portion 102D via the rod portion 105D. The rod portion 105D includes a valve flange 106D, a rod flange 107, and a rod 108. The valve flange 106D is made of a conductive material (such as Kovar, etc.) and has a cylindrical shape. The rod flange 107 is embedded and fixed in the valve flange 106D. The valve flange 106D is connected to the end portion of the rear side of the valve portion 102D.

[0098] In the X-ray tube 10D of the present modification, the line of sight from the X-ray generation position P toward the valve portion 102D can also be blocked by the second grid electrode 124. Therefore, the X-ray tube 10D can block the X-rays from the X-ray generation position P toward the valve portion 102D by the second grid electrode 124, and can suppress the incidence of the X-rays on the valve portion 102D, similarly to the X-ray tube 10 of the embodiment.

[0099] Although various embodiments and modifications of the present invention have been described above, the present invention is not limited to the above embodiments and modifications. For example, at least a part of the above various embodiments and various modifications may be arbitrarily combined.

[0100] For example, Figure 7 The X-ray tube 10D of the fourth modified example shown in FIG. Figure 5 The X-ray tube 10B shown in FIG. 1 is a reflection type X-ray tube. Figure 7 The X-ray tube 10D of the fourth modified example shown in FIG. Figure 6 As in the X-ray tube 10C shown in the figure, the target support body on which the target T is set is held by a holding valve made of an insulating material.

[0101] The second grid electrode may also block the line of sight from the X-ray generating position to the valve portion by a structure other than having the convex portion 124b as in the second grid electrode 124 and having a tapered shape as in the second grid electrode 126. For example, the second grid electrode may be thickened as a whole, rather than having a part of the wall thickened by the convex portion 124b as in the second grid electrode 124 of the embodiment.

[0102] Explanation of symbols

[0103] 10, 10A, 10B, 10C, 10D: X-ray tube

[0104] 100, 100C, 100D: Vacuum frame

[0105] 101, 101B: Head (metal frame)

[0106] 102, 102D: Valve

[0107] 110: Electron gun department

[0108] 124, 126, 126A: second grid electrode (focusing electrode portion)

[0109] 124b: convex part

[0110] 141: Frame part (metal frame part)

[0111] F1: Outer surface

[0112] F2: End face

[0113] K1~K4: Corner

[0114] T: Target

[0115] XR: X-ray.

Claims

1. An X-ray tube, wherein: The invention comprises: an electron gun unit that emits electrons; a target that generates X-rays by the incidence of the electrons; and a vacuum frame unit that accommodates the electron gun unit and the target. The vacuum frame portion has: a metal frame portion that supports the target; and a valve portion, which is made of an insulating material and connected to the metal frame portion, The electron gun unit has a cylindrical focusing electrode unit at an end portion on the electron emission side for focusing the emitted electrons, and is supported by the valve unit in such a manner that at least a portion of the focusing electrode unit is located within the metal frame unit. When viewed from the X-ray generating position of the target, the focusing electrode portion blocks the line of sight from the X-ray generating position to the valve portion. The focusing electrode portion has a convex portion protruding toward the outside, The wall thickness of the convex portion of the focusing electrode is thicker, The electron gun unit includes: an electron gun frame unit, which is a cylindrical shape made of conductive material, one end of which is connected to the focusing electrode unit to form a power supply path for the focusing electrode unit, and the other end is connected to a rod unit. The electron gun unit is supported by the valve unit via the rod unit, and the rod unit is provided at an opening at one end of the valve unit in a manner to seal the opening.

2. The X-ray tube according to claim 1, wherein: The convex portion is provided on an end portion on the target side of the outer peripheral surface of the focusing electrode portion.

3. The X-ray tube according to claim 1, wherein: Corners of the protrusions are rounded in a curved manner.

4. An X-ray tube, wherein: The invention comprises: an electron gun unit that emits electrons; a target that generates X-rays by the incidence of the electrons; and a vacuum frame unit that accommodates the electron gun unit and the target. The vacuum frame portion has: a metal frame portion that supports the target; and a valve portion, which is made of an insulating material and connected to the metal frame portion, The electron gun unit has a cylindrical focusing electrode unit at an end portion on the electron emission side for focusing the emitted electrons, and is supported by the valve unit in such a manner that at least a portion of the focusing electrode unit is located within the metal frame unit. When viewed from the X-ray generating position of the target, the focusing electrode portion blocks the line of sight from the X-ray generating position to the valve portion. The outer peripheral surface of the focusing electrode portion is in a tapered shape with a larger diameter as it approaches the target. The wall thickness of the focusing electrode becomes thicker as it moves toward the target side. The electron gun unit includes: an electron gun frame unit, which is a cylindrical shape made of conductive material, one end of which is connected to the focusing electrode unit to form a power supply path for the focusing electrode unit, and the other end is connected to a rod unit. The electron gun unit is supported by the valve unit via the rod unit, and the rod unit is provided at an opening at one end of the valve unit in a manner to seal the opening.

5. The X-ray tube according to claim 4, wherein: A corner between an outer peripheral surface of the focusing electrode portion and an end surface of the focusing electrode portion on the target side is rounded in a curved manner.

Images