X-ray tube, and method for manufacturing target

Abstract

To provide an X-ray tube that can prevent radiation heat from a target from being incident on a rotation part, and a method for manufacturing a target.SOLUTION: An X-ray tube according to an embodiment comprises: an envelope that can maintain an atmosphere with a reduced pressure compared to the atmospheric pressure; a rotary shaft that is rotatably provided inside the envelope; a target that is provided at one end of the rotary shaft inside the envelope, and has a first surface and a second surface facing the first surface; and a cathode that is provided inside the envelope, and faces the first surface of the target. The second surface of the target is provided with a plurality of radiation control parts exhibiting micron order projections and projecting in substantially the same directions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments of the present invention relate to an X-ray tube and a method for manufacturing a target. [Background technology]

[0002] X-ray tubes that generate X-rays are installed in medical equipment that uses X-rays to diagnose subjects and in industrial equipment that uses X-rays to inspect, measure, and analyze objects. One type of X-ray tube is a rotating anode X-ray tube. A rotating anode X-ray tube includes, for example, a cathode that emits thermoelectrons, a target facing the cathode, and a rotating part that rotates the target. The thermoelectrons emitted from the cathode are accelerated and focused by the potential gradient between the cathode and the target, and then collide with the target. X-rays are generated when the thermoelectrons collide with the target, and the generated X-rays are emitted outside the X-ray tube.

[0003] Here, about 1% of the kinetic energy of the thermoelectrons that collide with the target is converted into X-rays, and the remaining energy is converted into heat. As a result, the temperature of the target becomes very high. The heat from the heated target is then released to the outside by radiation. In this case, the rotating part that rotates the target is located near the target, so the temperature of the rotating part is likely to rise due to the radiant heat from the target. If the temperature of the rotating part becomes too high, thermal deformation such as eccentricity will occur in the rotating part, which may result in vibration or damage.

[0004] Therefore, there has been a demand for the development of a technology that can prevent radiant heat from the target from being incident on the rotating part. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-340148 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide an X-ray tube capable of suppressing radiant heat from the target from entering the rotating part, and a method for manufacturing the target. [Means for solving the problem]

[0007] An X-ray tube according to an embodiment includes an envelope capable of maintaining an atmosphere reduced in pressure below atmospheric pressure, a rotating shaft rotatably provided inside the envelope, a target provided at one end of the rotating shaft inside the envelope and having a first surface and a second surface opposite the first surface, and a cathode provided inside the envelope and facing the first surface of the target. The second surface of the target is provided with a plurality of radiation control portions each having a protrusion on the order of microns and protruding in approximately the same direction. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic cross-sectional view illustrating an X-ray tube according to an embodiment of the present invention. [Figure 2] 10 is a micrograph of a plurality of radiation control portions. [Figure 3] FIG. 2 is a schematic diagram of a plurality of radiation control sections. [Figure 4] This is an experimental device for verifying the direction of heat radiation in the radiation control section. [Figure 5] 10 is a table illustrating measurement results of emissivity. [Figure 6] 10A and 10B are schematic cross-sectional views illustrating targets according to other embodiments. [Figure 7] FIG. 10 is a schematic cross-sectional view illustrating a radiation control section according to another embodiment. [Figure 8] 10(a) to 10(c) are schematic cross-sectional views illustrating the steps of forming a plurality of radiation controlling portions. [Figure 9] 10A and 10B are schematic plan views for illustrating the movement of the laser irradiation position. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be illustrated with reference to the drawings. In the drawings, like components are designated by like reference numerals and detailed descriptions thereof will be omitted where appropriate.

[0010] FIG. 1 is a schematic cross-sectional view illustrating an X-ray tube 1 according to the present embodiment. As shown in FIG. 1, the X-ray tube 1 includes, for example, an envelope 2, a cathode 3, and an anode 4.

[0011] The envelope 2 has an airtight structure that can maintain an atmosphere at a pressure lower than atmospheric pressure. The envelope 2 has, for example, a first portion 21 and a second portion 22. The first portion 21 and the second portion 22 are arranged side by side in a direction along the central axis 2a of the envelope 2. The first portion 21 and the second portion 22 are joined so as to be substantially coaxial and airtight.

[0012] The first portion 21 and the second portion 22 are, for example, substantially cylindrical. In a direction intersecting the central axis 2a of the envelope 2, the dimension (radial dimension) of the first portion 21 is larger than the dimension (radial dimension) of the second portion 22.

[0013] The first section 21 accommodates, for example, the cathode 3 and a target 44 attached to the anode 4. A transmission window 23 that allows X-rays 200 to pass through is provided on the side wall of the first section 21. The transmission window 23 is airtightly bonded to the side wall of the first section 21 so as to cover a hole provided in the side wall of the first section 21. The second portion 22 accommodates, for example, a fixed shaft 41, a rotating shaft 42, and a fluid bearing 43 provided in the anode 4.

[0014] The first portion 21 and the second portion 22 are made of, for example, metal. The first portion 21 and the second portion 22 can be joined together using, for example, a glass material.

[0015] The cathode 3 is provided inside the envelope 2 and faces the first surface 44 b of the target 44 . The cathode 3 includes, for example, a cathode assembly 31 and a filament 32 . The cathode assembly 31 extends, for example, in a direction intersecting the central axis 2a of the envelope 2. The cathode assembly 31 is not necessarily required and can be omitted. For example, the filament 32 can be provided on the inner wall of the first portion 21 of the envelope 2.

[0016] The filament 32 is provided near the end of the cathode assembly 31 opposite to the central axis 2a of the envelope 2. In the direction along the central axis 2a of the envelope 2, the filament 32 is provided at a position facing the target layer 44d of the target 44. The filament 32 is made of, for example, tungsten. It should be noted that, for example, a flat emitter may be provided in place of the filament 32. In other words, the cathode 3 may be anything that can emit thermoelectrons 32a.

[0017] The anode 4 includes, for example, a fixed shaft 41 , a rotating shaft 42 , a fluid bearing 43 , and a target 44 .

[0018] The fixed shaft 41 is columnar and extends in a direction along the central axis 2a of the envelope 2. The fixed shaft 41 can be provided, for example, so as to be approximately coaxial with the central axis 2a of the envelope 2. One end of the fixed shaft 41 is exposed from the end of the second portion 22 of the envelope 2. A high-voltage power supply can be electrically connected to one end of the fixed shaft 41. The other end of the fixed shaft 41 can be provided, for example, inside the first portion 21 of the envelope 2. The fixed shaft 41 is formed from a metal such as an iron alloy or a molybdenum alloy.

[0019] The rotating shaft 42 is rotatably provided inside the envelope 2. The rotating shaft 42 is columnar and extends in a direction along the central axis 2a of the envelope 2. One end of the rotating shaft 42 can be provided inside the second portion 22 of the envelope 2. A recess 42a opens at one end of the rotating shaft 42. The recess 42a extends along the central axis 42c of the rotating shaft 42. A fixed shaft 41 is provided inside the recess 42a. A predetermined gap is provided between the inner wall of the recess 42a and the fixed shaft 41. The other end of the rotating shaft 42 can be provided inside the first portion 21 of the envelope 2. The rotating shaft 42 is formed of a metal such as an iron alloy or a molybdenum alloy. The central axis of the fixed shaft 41 and the central axis 42c of the rotating shaft 42 may be substantially coaxial with the central axis 2a of the envelope 2, for example.

[0020] The fluid bearing 43 is provided in the gap between the inner wall of the recess 42a and the fixed shaft 41. The fluid bearing 43 functions as a dynamic pressure sliding bearing when the rotating shaft 42 rotates. The fluid bearing 43 also electrically connects the fixed shaft 41 and the rotating shaft 42, and further, the fixed shaft 41 and the target 44. The fluid bearing 43 can be made of, for example, a gallium-indium alloy or a gallium-indium-tin alloy.

[0021] The target 44 is, for example, disk-shaped and has a first surface 44b and a second surface 44c opposite the first surface 44b. The target 44 is provided inside the enclosure 2 at one end of the rotating shaft 42. For example, the target 44 is provided at the end of the rotating shaft 42 opposite the side where the recess 42a opens. The target 44 can be detachably provided at the end of the rotating shaft 42. For example, a hole 44a penetrating between the first surface 44b and the second surface 44c can be provided at the center of the target 44, and the end of the rotating shaft 42 can be provided inside the hole 44a. The target 44 can then be attached to the end of the rotating shaft 42 using a fastening member such as a nut 42b.

[0022] The peripheral region of the first surface 44b of the target 44 forms an inclined surface 44b1. The inclined surface 44b1 faces the filament 32 of the cathode 3. The inclined surface 44b1 is inclined in a direction away from the filament 32 as it approaches the periphery of the target 44. A target layer 44d can be provided on the inclined surface 44b1.

[0023] The target 44 can be formed from, for example, molybdenum, tungsten, or an alloy containing these. The melting point of the material of the target layer 44d can be the same as or higher than the melting point of the material of the target 44. For example, the material of the target 44 can be molybdenum or a molybdenum alloy, and the material of the target layer 44d can be tungsten or a tungsten alloy. Furthermore, for example, the material of the target 44 and the material of the target layer 44d can be tungsten or a tungsten alloy. Note that if the material of the target 44 and the material of the target layer 44d are the same, the target layer 44d can be omitted.

[0024] As shown in Fig. 1, a stator coil 100 is provided outside the enclosure 2. The stator coil 100 has an annular shape and surrounds the rotating shaft 42 via the second portion 22 of the enclosure 2. When a current flows through the stator coil 100, a magnetic field is generated, which rotates the rotating shaft 42. As a result, the target 44 rotates together with the rotating shaft 42.

[0025] Furthermore, a negative voltage is applied to the filament 32, and a positive voltage is applied to the fixed shaft 41. When a negative voltage is applied to the filament 32, thermoelectrons 32a are emitted from the filament 32. When a positive voltage is applied to the target 44 via the fixed shaft 41, the fluid bearing 43, and the rotating shaft 42, a potential difference is generated between the filament 32 and the target 44. Therefore, the generated potential gradient causes the thermoelectrons 32a to be accelerated and focused, and to collide with the target layer 44d of the target 44. When the thermoelectrons 32a collide with the target layer 44d, X-rays 200 are generated, and the generated X-rays 200 are emitted to the outside of the X-ray tube 1 through the transmission window 23.

[0026] Here, about 1% of the kinetic energy of the thermoelectrons 32a colliding with the target layer 44d of the target 44 is converted into X-rays 200, and the remaining energy is converted into heat. As a result, the temperature of the target 44 becomes high. The heat of the target 44 that has reached a high temperature is released into the inside of the first part 21 of the envelope 2 by radiation.

[0027] 1, a fixed shaft 41, a rotating shaft 42, and a fluid bearing 43 are provided near the target 44. Therefore, the temperatures of the fixed shaft 41, the rotating shaft 42, and the fluid bearing 43 may become too high due to radiant heat from the target 44. In this case, if thermal deformation such as eccentricity occurs in at least one of the fixed shaft 41 and the rotating shaft 42, vibration of the target 44 or damage or malfunction of at least one of the fixed shaft 41 and the rotating shaft 42 may occur.

[0028] Therefore, as shown in FIG. 1, the second surface 44c of the target 44 is provided with a plurality of radiation control portions 44e. FIG. 2 is a micrograph of a plurality of radiation controlling portions 44e. FIG. 3 is a schematic diagram of a plurality of radiation control sections 44e. 2 and 3, the radiation control parts 44e have a protruding shape. The radiation control parts 44e protrude in approximately the same direction. In this specification, "approximately the same direction" does not only mean the same direction, but also includes deviations due to, for example, manufacturing errors.

[0029] The pitch dimension P of the plurality of radiation control parts 44e can be set to, for example, about 10 μm to 100 μm. The height H of the radiation control parts 44e can be set to, for example, about 10 μm to 500 μm. That is, the radiation control parts 44e have protrusions on the order of microns, and protrude in substantially the same direction (the protruding directions are substantially the same).

[0030] The shape of the radiation control portion 44e is not particularly limited as long as it is a protrusion on the order of microns. In the shape of the radiation control portion 44e illustrated in Figs. 2 and 3, the dimension of the radiation control portion 44e in a direction intersecting the protruding direction becomes smaller toward the tip. For example, the shape of the radiation control portion 44e can be a substantially truncated pyramid or a truncated cone. The shape of the radiation control portion 44e may be such that the dimension of the radiation control portion 44e in a direction intersecting the protruding direction is substantially constant. For example, the shape of the radiation control portion 44e can be a substantially prismatic or cylindrical shape.

[0031] If multiple radiation control parts 44e with micron-order protrusions protrude in approximately the same direction, more heat can be radiated in the protruding direction of the radiation control parts 44e. In other words, the heat radiation direction can be made directional.

[0032] FIG. 4 shows an experimental device 300 for verifying the direction of heat radiation in the radiation control section 44e. The test piece 301 used in the experiment was formed as follows. First, one surface of a flat plate material containing molybdenum is irradiated with a laser pulse for a certain period of time to form a recessed portion that opens into the surface of the flat plate material. Next, the laser irradiation position is shifted by a predetermined distance, and one surface of the flat plate is irradiated with pulsed laser light for a certain period of time, thereby forming a recess that opens into the surface of the flat plate. By repeating the above procedure, test piece 301 was formed, which had a plurality of radiation controlling portions 44e protruding in approximately the same direction. In the test piece 301 thus formed, the plurality of radiation control parts 44e protrude in a direction substantially perpendicular to the surface of the flat plate material.

[0033] The laser irradiation conditions when forming the plurality of radiation control portions 44e are an output of 6.4 W (watts), a pulse width of 245 fs (fetoseconds), a scanning speed of 3000 mm / s, and an irradiation pitch of 40 μm.

[0034] As shown in FIG. 4, the experimental device 300 is provided with a hot plate 302, a temperature sensor 303, and a thermoviewer 304. The test piece 301 was placed on the hot plate 302. At this time, the surface of the test piece 301 on which the plurality of radiation control parts 44e were provided was oriented opposite to the hot plate 302 side. The temperature sensor 303 was a sheet-like thermocouple, and was sandwiched between the test piece 301 and the hot plate 302 to measure the temperature of the test piece 301 . The thermoviewer 304 measured the emissivity (radiation rate) of infrared rays radiated from the test piece 301 by changing the angle of the test piece 301 with respect to the surface on which the plurality of radiation control sections 44e were provided.

[0035] For example, as shown in FIG. 4, the infrared emissivity (heat emissivity in the direction in which the multiple radiation control units 44e protrude) of the test piece 301 was measured in measurement direction A, which is a direction perpendicular to the surface on which the multiple radiation control units 44e are provided. As measurement direction B, the infrared emissivity (heat emissivity in a direction inclined 45° from the direction perpendicular to the surface of test piece 301 on which multiple radiation control sections 44e are provided) was measured. As measurement direction C, the infrared emissivity (heat emissivity in a direction inclined 60° from the direction perpendicular to the surface of test piece 301 on which multiple radiation control sections 44e are provided) was measured.

[0036] FIG. 5 is a table illustrating the measurement results of the emissivity. 5, the emissivity of infrared rays in measurement direction A is higher than the emissivity of infrared rays in measurement directions B and C. This means that the emissivity of heat in the direction in which the multiple radiation control parts 44e protrude is higher than the emissivity of heat in a direction tilted from the direction in which the multiple radiation control parts 44e protrude.

[0037] Therefore, by providing multiple radiation control parts 44e on the second surface 44c of the target 44, it is possible to control the radiation direction of the heat radiated from the second surface 44c of the target 44 by the protruding direction of the multiple radiation control parts 44e.

[0038] For example, as shown in FIG. 1, by making the multiple radiation control parts 44e protrude in a direction substantially perpendicular to the second surface 44c of the target 44, much of the heat radiated from the target 44 can be released in a direction substantially perpendicular to the second surface 44c of the target 44. This reduces the amount of radiant heat radiated from the second surface 44c of the target 44 and incident on the rotating shaft 42. Reducing the amount of radiant heat incident on the rotating shaft 42 can prevent thermal deformation, such as eccentricity, from occurring in at least one of the fixed shaft 41 and the rotating shaft 42. This can prevent vibration of the target 44 and damage or malfunction of at least one of the fixed shaft 41 and the rotating shaft 42.

[0039] Furthermore, when viewed from a direction along the central axis 42c of the rotating shaft 42, the multiple radiation control parts 44e can be provided on the second surface 44c of the target 44 outside the area that overlaps with the rotating shaft 42. In this way, it is possible to effectively prevent radiant heat from being incident on the rotating shaft 42.

[0040] FIG. 6 is a schematic cross-sectional view illustrating a target 144 according to another embodiment. 6, the target 144 is, for example, disk-shaped and has a first surface 44b and a second surface 144c opposite the first surface 44b. A hole 44a is provided in the center of the target 44, penetrating between the first surface 44b and the second surface 144c. The end of the rotating shaft 42 can be provided inside the hole 44a. The target 144 can be attached to the end of the rotating shaft 42 using a fastening member such as a nut 42b.

[0041] As shown in FIG. 1, the second surface 44c of the target 44 is approximately perpendicular to the central axis 42c of the rotating shaft 42, and multiple radiation control portions 44e protrude in a direction approximately perpendicular to the second surface 44c of the target 44.

[0042] In contrast, in the case of target 144 according to the present embodiment, at least the region on the outer edge side of second surface 144c is an inclined region 144ca that inclines in a direction approaching first surface 44b as it approaches the outer edge of second surface 144c. Note that target 144 can be similar to target 44 except for being provided with inclined region 144ca.

[0043] When viewed from a direction along the central axis 42c of the rotary shaft 42, the inclined region 144ca can be provided at least outside the region overlapping with the rotary shaft 42. Note that the entire second surface 144c may be the inclined region 144ca.

[0044] The radiation control parts 44e are provided in the inclined region 144ca and protrude in a direction approximately perpendicular to the inclined region 144ca. When the entire second surface 144c is the inclined region 144ca, the radiation control parts 44e can be provided outside the region overlapping with the rotating shaft 42 when viewed from a direction along the central axis 42c of the rotating shaft 42.

[0045] In this way, the plurality of radiation control parts 44e can be made to protrude outward from the rotating shaft 42. This makes it easy to dissipate most of the heat radiated from the target 144 in the outward direction of the rotating shaft 42. As a result, the amount of radiant heat radiated from the second surface 144c of the target 144 and incident on the rotating shaft 42 can be reduced. Reducing the amount of radiant heat incident on the rotating shaft 42 can effectively prevent thermal deformation, such as eccentricity, from occurring in at least one of the fixed shaft 41 and the rotating shaft 42. This can effectively prevent vibration of the target 44 and damage or malfunction of at least one of the fixed shaft 41 and the rotating shaft 42.

[0046] FIG. 7 is a schematic cross-sectional view illustrating a radiation control portion 144e according to another embodiment. As shown in FIG. 7, the radiation control portions 144e have protrusions on the order of microns and protrude in approximately the same direction. The radiation control portions 144e are provided on the second surface 44c of the target 44. The radiation control portions 144e protrude outward from the rotating shaft 42. For example, the radiation control portions 144e protrude at an angle in a direction away from the central axis 42c of the rotating shaft 42 as they approach the tip. The radiation control portions 144e can be similar to the radiation control portion 44e described above, except that they protrude outward from the rotating shaft 42. The radiation control portions 144e can also be provided in the inclined region 144ca of the second surface 144c illustrated in FIG. 6.

[0047] When viewed from a direction along the central axis 42c of the rotating shaft 42, the tips of the multiple radiation control portions 144e can be provided on the outside of the area of ​​the second surface 44c of the target 44 that overlaps with the rotating shaft 42. Furthermore, when viewed from a direction along the central axis 42c of the rotating shaft 42, the multiple radiation control portions 144e can also be provided on the outside of the area of ​​the second surface 44c of the target 44 that overlaps with the rotating shaft 42.

[0048] If the radiation control portion 144e protrudes toward the outside of the rotating shaft 42, it becomes easy to dissipate most of the heat radiated from the target 44 in the direction toward the outside of the target 44. As a result, it is possible to reduce the amount of radiant heat radiated from the second surface 44c of the target 44 and incident on the rotating shaft 42. If the amount of radiant heat incident on the rotating shaft 42 is reduced, it is possible to effectively prevent thermal deformation such as eccentricity from occurring in at least one of the fixed shaft 41 and the rotating shaft 42. Therefore, it is possible to effectively prevent vibration of the target 44 and damage or malfunction of at least one of the fixed shaft 41 and the rotating shaft 42.

[0049] Next, a method for manufacturing a target according to this embodiment will be illustrated. First, the main body 244 of the target 44 is formed, which has a first surface 44b and a second surface 44c opposite to the first surface 44b. Known techniques can be applied to the formation of the main body 244 of the target 44, and therefore detailed description thereof will be omitted.

[0050] Next, a plurality of radiation control portions 44e are formed on the second surface 44c of the main body 244 of the target 44. Here, the convex portions having micron-order protrusions can also be formed by, for example, performing a blasting process on the second surface 44c of the main body 244 of the target 44. However, when the convex portions having micron-order protrusions are formed in this manner, the protrusion directions of the convex portions become random (the convex portions do not protrude in approximately the same direction). When the protrusion directions of the convex portions become random, it becomes difficult to impart directionality to the heat radiation direction.

[0051] Therefore, in the method for manufacturing a target according to the present embodiment, a plurality of radiation control portions 44e are formed as follows. 8(a) to 8(c) are schematic cross-sectional process views illustrating the formation of a plurality of radiation controlling portions 44e.

[0052] 8(a), a laser beam 400 is pulsed for a certain period of time onto the second surface 44c of the main body 244 of the target 44. For example, the laser beam 400 can be irradiated onto the second surface 44c from a direction perpendicular to the second surface 44c. The irradiation conditions of the laser 400 are, for example, an output of about 6.4 W (watts) and a pulse width of about 245 fs (femtoseconds).

[0053] Next, as shown in FIG. 8(b), the material of the main body 244 is evaporated at the position irradiated with the laser 400, and a recess 44c1 opening to the second surface 44c of the main body 244 is formed. Furthermore, particles 244a of the evaporated material of the main body 244 are suspended near the opening of the recess 44c1. 8(c), after the recess 44c1 is formed, the irradiation of the laser 400 is stopped. When the irradiation of the laser 400 is stopped, a plurality of particles 244a are deposited on the second surface 44c near the opening of the recess 44c1 and on the inner wall of the recess 44c1. The deposited plurality of particles 244a and the recess 44c1 form a radiation control portion 44e.

[0054] Next, the irradiation position of the laser 400 is moved a predetermined distance, and the laser 400 is irradiated onto the second surface 44c in the same manner as in FIG. 8(a). FIG. 9 is a schematic plan view illustrating the movement of the irradiation position of the laser 400. In FIG. The scanning speed of the laser 400 is, for example, about 3000 mm / s, and the irradiation pitch P (movement distance of the irradiation position) is about 40 μm.

[0055] 9 illustrates an example in which the irradiation positions of the laser 400 are arranged in a staggered pattern, but the irradiation positions of the laser 400 may be any positions. For example, the irradiation positions of the laser 400 may be arranged in a matrix pattern or a radial pattern. The irradiation position of the laser 400 can also be random. However, if the irradiation positions of the laser 400 are arranged with some regularity, such as in a staggered, matrix, or radial pattern, it becomes easier to provide many radiation control units 44e, 144e in a predetermined area and to suppress variations in radiation characteristics.

[0056] When the irradiation position of the laser 400 is moved by a predetermined irradiation pitch P, a recess 44c1 opening on the second surface 44c of the main body 244 is formed, as in FIG. 8(b). Furthermore, when the irradiation of the laser 400 is stopped after the recess 44c1 is formed, a plurality of particles 244a are deposited near the opening of the recess 44c1 and on the inner wall of the recess 44c1.

[0057] By repeating the above procedure, it is possible to form a plurality of radiation controlling portions 44e that protrude in approximately the same direction and have micron-order protrusions, as shown in FIG. 8(c) and FIG.

[0058] 6, a plurality of radiation control portions 44e may be provided in the inclined region 144ca of the second surface 144c. In such a case, the inclined region 144ca may be irradiated with the laser 400 from a direction perpendicular to the inclined region 144ca.

[0059] 7, there may be provided a plurality of radiation control portions 144e that are inclined toward the outside of the rotary shaft 42. In such a case, the laser 400 may be irradiated onto the second surface 44c from a direction inclined at a predetermined angle with respect to the second surface 44c. For example, a reflecting mirror or the like may be used to tilt the irradiation direction of the laser 400 or to tilt the second surface 44c.

[0060] As described above, in the method for manufacturing a target according to this embodiment, the main body 244 of the target 44 is formed, which has a first surface 44b and a second surface 44c opposite the first surface 44b, and the second surface 44c is irradiated with a laser 400 to form a plurality of radiation control portions 44e, 144e having protrusions on the order of microns and protruding in approximately the same direction.

[0061] Although the embodiments have been described above, the present invention is not limited to these descriptions. Any design modifications made by a person skilled in the art to the above-described embodiments are also encompassed within the scope of the present invention as long as they include the features of the present invention. For example, the shape, size, material, arrangement, etc. of each element included in the X-ray tube 1 are not limited to those exemplified, and can be changed as appropriate. Furthermore, the elements of each of the above-described embodiments can be combined to the greatest extent possible, and such combinations are also included within the scope of the present invention as long as they include the features of the present invention. [Explanation of symbols]

[0062] 1 X-ray tube, 2 envelope, 3 cathode, 4 anode, 32 filament, 41 fixed shaft, 42 rotating shaft, 42c central axis, 43 fluid bearing, 44 target, 44b first surface, 44c second surface, 44d target layer, 44e radiation control portion, 144e radiation control portion, 244 main body, 400 laser

Claims

1. an envelope capable of maintaining an atmosphere reduced in pressure below atmospheric pressure; a rotating shaft rotatably provided inside the enclosure; a target provided at one end of the rotary shaft within the enclosure, the target having a first surface and a second surface opposite to the first surface; a cathode provided inside the envelope and facing the first surface of the target; Equipped with An X-ray tube, wherein the second surface of the target is provided with a plurality of radiation control portions, each having a protrusion shape on the order of microns and protruding in approximately the same direction.

2. 2. The X-ray tube according to claim 1, wherein, when viewed from a direction along the central axis of the rotating shaft, the plurality of radiation control portions are provided on the second surface of the target outside an area that overlaps with the rotating shaft.

3. 3. The X-ray tube according to claim 1, wherein the dimension of the radiation control portion in a direction intersecting the protruding direction decreases toward the tip end.

4. 3. The X-ray tube according to claim 1, wherein the plurality of radiation control portions protrude in a direction substantially perpendicular to the second surface of the target, or protrude at an angle in a direction away from the central axis of the rotating shaft as they approach the tip end.

5. At least an outer edge side region of the second surface of the target is an inclined region that inclines toward the first surface as it approaches the outer edge of the second surface, The X-ray tube according to claim 1 , wherein the plurality of radiation control portions are provided in the inclined region.

6. forming a target body having a first surface and a second surface opposite the first surface; A method for manufacturing a target in which a laser is irradiated onto the second surface to form a plurality of radiation control portions that have micron-order protrusions and protrude in approximately the same direction.

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