Structure, x-ray generating device, and method for manufacturing heat radiation unit

Abstract

To provide a structure with improved heat radiation properties.SOLUTION: A structure is heated to 700°C or more, and has a heat radiation unit that radiates heat of the structure. The heat radiation unit has, on its surface, a first uneven structure in which a plurality of first projections and a plurality of first recesses are alternately arranged. A peak wavelength of electromagnetic waves thermally radiated from the heat radiation unit is 3 μm or less. The distance between first projections adjacent to each other of the plurality of first projections, or the distance between first recesses adjacent to each other of the plurality of first recesses, is less than 1 / 2 of the peak wavelength.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a structure, an X-ray generating device, and a method for manufacturing a heat dissipation part. [Background technology]

[0002] For parts that become hot during use, technology that improves heat dissipation may be applied to reduce the amount of heat stored. For example, there is technology that increases light absorption and improves heat dissipation by making the surface of the part out of black material or painting or spraying black material.

[0003] Moreover, Patent Document 1 discloses a configuration in which fins are provided on the surface of a target for an X-ray tube. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication WO2020 / 067075 Summary of the Invention [Problem to be solved by the invention]

[0005] The configuration of Patent Document 1 does not have sufficient heat dissipation properties, and there is room for improvement in heat dissipation properties on the surface of the components.

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a structure having improved heat dissipation properties. [Means for solving the problem]

[0007] The means for solving the above problem is a structure that is heated to 700°C or higher, and has a heat dissipation section that dissipates heat from the structure, and a first uneven structure in which a plurality of first convex sections and a plurality of first concave sections are alternately arranged on the surface of the heat dissipation section, the peak wavelength of electromagnetic waves radiated from the heat dissipation section is 3 μm or less, and the distance between adjacent first convex sections among the plurality of first convex sections, or the distance between adjacent first concave sections among the plurality of first concave sections, is less than 1 / 2 of the peak wavelength. Effect of the Invention

[0008] According to the structure of the present invention, heat dissipation properties can be improved. [Brief description of the drawings]

[0009] [Figure 1] Schematic diagram of an X-ray generator (rotating anode X-ray tube). [Diagram 2] FIG. 2(a) is an enlarged view showing an electron tube target and an electron emission source in the X-ray generating device of FIG. 1, and FIG. 2(b) is an enlarged view of a portion surrounded by a circle C in FIG. 2(a). [Diagram 3] 1 is a schematic diagram of a laser processing machine for manufacturing a heat dissipation portion. FIG. [Figure 4] 10 is a flowchart illustrating steps for laser processing a heat dissipation portion. [Diagram 5] 1 is a schematic diagram of a CT device to which the X-ray generating device of this embodiment is applied. [Figure 6] FIG. 11 is a diagram illustrating a target according to a second embodiment. [Figure 7] FIG. 7(a) is an enlarged photograph of the surface of the component before heat treatment, and FIG. 7(b) is an enlarged photograph of the surface of the component after heat treatment. [Figure 8] FIG. 8(a) is an SEM photograph (a substitute for a drawing) of FIG. 7(a) enlarged further, and FIG. 8(b) is an SEM photograph (a substitute for a drawing) of FIG. 7(b) enlarged further. [Figure 9] FIG. 13 is a diagram showing how a first uneven structure is formed on a heat dissipation portion by using dry etching. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiment for carrying out the present invention will be described with reference to the drawings. However, the embodiment described below is one embodiment of the invention, and the present invention is not limited to this. Then, common configurations will be described with mutual reference to multiple drawings, and the description of configurations with common symbols will be omitted as appropriate. Items with the same name but different can be distinguished by adding "No. 0", such as the first item and the second item.

[0011] First Embodiment The structure according to this embodiment will be described with reference to Fig. 1 and Fig. 2. This embodiment shows an example in which a target for an electron tube of an X-ray generating device constitutes the structure. Fig. 1 is a schematic diagram of an X-ray generating device (rotating anode X-ray tube). Fig. 2(a) is an enlarged view showing the target for an electron tube and an electron emission source in the X-ray generating device of Fig. 1, and Fig. 2(b) is an enlarged view of a portion surrounded by a circle C in Fig. 2(a).

[0012] 1, an X-ray generating device 100 has an electron emission source 11 provided on a cathode assembly 12, and an electron tube target (hereinafter sometimes simply referred to as a target) 10 attached to an anode shaft 13. The electron emission source 11 constitutes a cathode, and the target 10 constitutes an anode. These members are housed in a vessel 14 that is kept in a vacuum state. Furthermore, the target 10 is rotated together with the anode shaft 13, for example, by a coil (not shown) provided outside the vessel.

[0013] An electron beam 15 emitted from the electron emission source 11 is focused by a focusing electrode (not shown) and irradiated onto the target 10. X-rays 16 are generated from the target 10 irradiated with the electron beam 15, and the generated X-rays 16 are radiated to the outside from the container 14.

[0014] At this time, part of the energy of the electron beam 15 irradiated onto the target 10 is used to generate X-rays, but most of the energy is absorbed by the target 10, causing the temperature of the target 10 to rise.

[0015] To emit high-power X-rays, it is necessary to irradiate a large amount of electron beams, and as a result, the target 10 is heated to a high temperature. Therefore, it is important to efficiently cool the target 10. However, since the target 10 is used in a vacuum, cooling by convection is difficult, and the target 10 is cooled by thermal radiation from the target 10 and thermal conduction through the anode shaft 13. In this embodiment, a heat dissipation section having an uneven structure is provided on the target 10, and a structure that efficiently radiates heat is configured.

[0016] The material for forming the target 10 is preferably a high-melting point metal that is easy to emit X-rays and has high heat resistance. In addition, in order to stabilize the emitted X-rays, a high-melting point metal with a large heat capacity is preferable so that the temperature fluctuation of the target 10 during irradiation with the electron beam can be suppressed. Therefore, it is preferable to use tungsten, molybdenum, niobium, tantalum, rhenium, hafnium, zirconium, yttrium, etc. as the material for the target 10.

[0017] On the other hand, the inside of the container 14 is preferably in a vacuum state. The degree of vacuum can range from a low vacuum (pressure of 1.0E5 Pa) to an absolute vacuum (pressure of 0 Pa) depending on the application. For example, in the case of the X-ray generating device 100 of this embodiment, the pressure is preferably 1.0E-4 Pa to 1.0E-6 Pa.

[0018] FIG. 2(a) shows an enlarged view of the main part of the X-ray generating device shown in FIG. 1. As described above, the target 10 is irradiated with an electron beam 15 from the electron emission source 11. Then, X-rays 16 are emitted from the target 10 irradiated with the electron beam 15. Meanwhile, heat is generated at an irradiation point 17 of the target 10 irradiated with the electron beam 15, and the target 10 is in a high-temperature state of 1000° C. or more. Therefore, in this embodiment, a heat dissipation section 20 having an uneven structure shown in FIG. 2(b) is provided on the outer surface of the target 10 to dissipate at least a part of the heat generated at the irradiation point 17. The heat dissipation section 20 may be provided on the entire outer surface of the target 10, or may be provided on a part of the outer surface. Here, the irradiation point 17 of the target 10 irradiated with the electron beam 15 corresponds to a "configuration that can be a heat source". In addition, since the electron beam 15 generates heat, the irradiation point 17 and the electron emission source 11 that irradiates the irradiation point 17 with the electron beam 15 can be considered as a "configuration that can be a heat source".

[0019] Next, the structure of the heat dissipation unit 20 will be described. FIG. 2(b) is an enlarged view of a portion surrounded by a circle C in FIG. 2(a). As shown in FIG. 2(b), the surface of the heat dissipation unit 20 of this embodiment has a first uneven structure 71 in which a plurality of first convex portions 710 and a plurality of first concave portions 711 are alternately arranged. The distance between adjacent first convex portions among the plurality of first convex portions 710, or the distance between adjacent first concave portions among the plurality of first concave portions 711, is formed to have a constant pitch P1. The distance between adjacent first convex portions is the distance from the top of a certain convex portion to the top of an adjacent convex portion. Similarly, the distance between adjacent first concave portions is the distance from the bottom of a certain concave portion to the bottom of an adjacent concave portion. In addition, a second uneven structure 72 in which a plurality of second convex portions 720 and a plurality of second concave portions 721 are alternately arranged is formed on the surface of the heat dissipation unit 20. The distance between adjacent second convex portions of the plurality of second convex portions 720, or the distance between adjacent second concave portions of the plurality of second concave portions 721, are formed to have a constant pitch P2. Here, the pitch P2 is longer than the pitch P1, and the first concave-convex structure 71 is formed on the surface of the second concave-convex structure 72.

[0020] In this embodiment, an example in which the pitch P1 and the pitch P2 are constant has been shown, but the distance between adjacent first convex portions or the distance between adjacent first concave portions (hereinafter referred to as distance L1) does not necessarily have to be constant. Similarly, the distance between adjacent second convex portions or the distance between adjacent second concave portions (hereinafter referred to as distance L2) does not necessarily have to be constant. In this case, the shortest distance among the distances L2 is formed to be longer than the longest distance among the distances L1.

[0021] In this embodiment, the distance L1 between the first convex portions or the first concave portions adjacent to each other in the first concave-convex structure 71 is formed to be less than 1 / 2 of the peak wavelength of the electromagnetic wave thermally radiated from the heat dissipation section 20. This configuration improves the heat dissipation performance of the heat dissipation section 20. On the other hand, if the distance L1 is 1 / 2 or more of the peak wavelength of the electromagnetic wave thermally radiated from the heat dissipation section 20, the heat dissipation performance of the heat dissipation section 20 will decrease. The reason for this is considered as follows. As will be described later, in order to efficiently radiate the electromagnetic wave of wavelength λ generated by thermal radiation, it is sufficient to consider a structure that can absorb the electromagnetic wave without reflecting it when an electromagnetic wave of the same wavelength λ as this electromagnetic wave is incident. Here, if the first concave-convex structure 71 is considered as a diffraction grating, the condition for no interference is that the pitch P1 of the first convex portions or the first concave portions is less than half the wavelength λ. This is a so-called subwavelength structure (hereinafter referred to as SWS), and is a structure that does not reflect the electromagnetic wave of wavelength λ.

[0022] Here, the peak wavelength of the electromagnetic wave varies depending on the temperature of the heat generating body that radiates heat, that is, the temperature of the target 10 (particularly the heat dissipation section 20) in this embodiment, and is, for example, 3.00 μm at 700° C., 2.47 μm at 900° C., 1.84 μm at 1300° C., 1.63 μm at 1500° C., and 1.55 μm at 1600° C. Therefore, it is desirable that the distance L1 between the adjacent first convex portions or the distance L1 between the first concave portions of the first uneven structure 71 be set depending on the situation in which the target 10 is used. For example, when the target 10 is used in a situation in which the temperature of the heat dissipation section 20 is 700° C., it is preferable that the distance L1 is less than 1 / 2 of 3.00 μm. In other words, it is preferable that the distance L1 is formed to be 50 nm or more and less than 1500 nm. Also, for example, when the heat dissipation section 20 is used in a situation in which the temperature is 900° C. to 1300° C., it is preferable to set the distance L1 based on the peak wavelength at 1300° C., which is the higher temperature. It is more preferable that the distance L1 is less than ¼ of the peak wavelength of the electromagnetic wave emitted as heat, for example, 200 nm or more and 600 nm or less.

[0023] On the other hand, the distance L2 between adjacent second convex portions or second concave portions in the second concave-convex structure 72 may be greater than the distance L1 in the first concave-convex structure 71. For example, the distance L2 is preferably 1 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less. This can improve the heat dissipation performance of the heat dissipation section 20.

[0024] The heat dissipation of the heat dissipation section 20 provided with the first uneven structure 71 and the second uneven structure 72 will be described below. The heat dissipation of the heat dissipation section 20 is correlated with the absorptivity of the heat dissipation section 20, and it can be said that a heat dissipation section with high absorptivity also has high heat dissipation. FIG. 2(b) shows an electromagnetic wave 73 incident on the heat dissipation section 20, a reflected electromagnetic wave 74, and a transmitted electromagnetic wave 75. When the pitch P1 of the first convex portion 710 or the first concave portion 711 of the first uneven structure 71 is less than 1 / 2 the peak wavelength of the electromagnetic wave to be radiated, the reflection of the incident electromagnetic wave 73 is reduced due to the effect of SWS, and the absorption rate of the electromagnetic wave 73 can be significantly improved. Therefore, from the relationship between the absorptivity and heat dissipation described above, the first uneven structure 71 can improve heat dissipation.

[0025] Meanwhile, a portion of the electromagnetic wave 73 incident on the heat dissipation section 20 is reflected into the second recess 721. The reflection of the reflected electromagnetic wave 74 is suppressed by the effect of the SWS of the first uneven structure 71 formed on the surface of the second uneven structure 72, but a portion of the reflected electromagnetic wave 74 is further reflected into the second recess 721. In this manner, the reflectance can be significantly reduced by the effect of the first uneven structure (SWS) on the surface and the holes in the second uneven structure 72. A reduction in reflectance leads to an increase in absorptance, and since a heat dissipation section with high absorptance also has high heat dissipation properties as described above, the provision of the second uneven structure 72 can further improve heat dissipation properties.

[0026] Such a mechanism for improving heat dissipation is also applicable when the distance L1 between adjacent first convex portions or first concave portions is not constant, such as the pitch P1. Also, when the distance L2 between adjacent second convex portions or second concave portions is not constant, such as the pitch P2, heat dissipation can be improved in a similar manner. In addition, in this embodiment, an example is shown in which the first uneven structure 71 is formed on the surface of the second uneven structure 72. However, the second uneven structure 72 does not necessarily need to be provided, and as long as the first uneven structure is formed, heat dissipation can be improved by the effect of SWS.

[0027] The shape of the first convex portion 710 or the first concave portion 711 constituting the first uneven structure 71 is not particularly limited, but it is preferable that the first convex portion 710 is formed from particles attached to the surface of the heat dissipation portion 20. By forming the first convex portion 710 in a shape in which particles are accumulated, the surface area becomes larger than other shapes, and the absorption rate of electromagnetic waves can be improved. In particular, in the target 10 used in an environment in which the temperature is 1000°C or higher, it is easy to form the first uneven structure 71 with a short pitch P1 by agglomerating the particles, and the effect of using it in combination with the second uneven structure 72 is large. When the first uneven structure 71 is in a form in which particles are accumulated, the particle diameter of the particles can be considered to correspond to the pitch P1 of the first uneven structure 71. Therefore, the particle diameter of the particles forming the first uneven structure 71 is formed to be smaller than 1 / 2 the peak wavelength of the electromagnetic wave to be emitted. Similarly, the depth of the first uneven structure 71 can be considered to correspond to the particle diameter of the particles.

[0028] The first uneven structure 71 is preferably formed from a metal that has a high X-ray radiation efficiency, a high melting point, and a large heat capacity. Here, a high melting point metal is a metal whose melting point is 1500° C. or higher. Tungsten is preferable as such a metal, and molybdenum, niobium, tantalum, rhenium, hafnium, zirconium, yttrium, and the like, which have a large heat capacity, are also suitable.

[0029] When the first uneven structure 71 is formed from a high melting point metal, it is preferable that the nitrogen content in a portion 100 nm or less from the surface of the first uneven structure 71 is 1 at% or more, or the oxygen content is 10 at% or less. For example, when the first uneven structure 71 is processed by the method described below, processing in a nitrogen atmosphere will incorporate 1 at% or more of nitrogen into the surface, which contributes to improving the emissivity. Furthermore, if a large amount of oxygen is contained in the high melting point metal, there is a risk that the melting point will decrease. Therefore, it is preferable that the oxygen content is 10 at% or less. However, the nitrogen content and oxygen content do not necessarily need to be within the above ranges, and may be within an appropriate range depending on the application.

[0030] Next, a manufacturing method of the heat dissipation section 20 according to this embodiment will be described with reference to FIGS. 3 and 4. FIG. 3 is a schematic diagram of a laser processing machine 110 for manufacturing the heat dissipation section 20. By using this laser processing machine 110 to cut the surface of a member such as the target 10 of this embodiment with a laser beam, a shape such as the second uneven structure 72 is processed in the heat dissipation section 20 (hereinafter, the target 10 may be referred to as a processed member, meaning a member on which the heat dissipation section 20 is formed). Meanwhile, the first uneven structure 71 is formed by depositing the cut metal particles on the surface of the second uneven structure 72 (see FIG. 2(b)). Therefore, the distance L1 between the first convex portions or the first concave portions adjacent to each other in the first uneven structure 71 is not constant. Furthermore, the particle size of the deposited metal particles does not need to be constant, and it is preferable that there are particles with a difference of 300 nm or more between the maximum particle size and the minimum particle size. Thereby, reflection can be generated randomly in the first uneven structure 71, and the absorptance in the first uneven structure 71 can be improved. Here, the particle size of the particles is preferably 50 nm or more and less than 1500 nm, and therefore the depth of the first uneven structure is preferably 50 nm or more and less than 1500 nm.

[0031] 3, the beam diameter of laser light emitted from a laser oscillator 111 is expanded by a beam expander 112. The laser light is then reflected by a galvanometer mirror 113, enters an Fθ lens 114, and is focused on a target (workpiece) 10 that forms the heat dissipation section 20. The target (workpiece) 10 is fixed to a fixed table 116 and can be freely moved by a moving stage 117.

[0032] The galvanometer control unit 118 controls the laser oscillator 111 and the galvanometer mirror 113. Although FIG. 3 shows an example in which one galvanometer mirror 113 is used, two mirrors are required to control the laser light in two axial directions, and the number of mirrors can be selected as appropriate depending on the application. The stage control unit 119 controls the moving stage 117. When performing autofocus, the moving stage 117 is controlled to move up and down based on a signal from a displacement meter (not shown) so that the distance between the laser focusing position and the target (workpiece) is constant. The host computer 120 includes a user interface and a processing data storage unit, and can control the galvanometer control unit 118 and the stage control unit 119 in a mutually linked manner at a predetermined timing. Although not shown, the moving stage 117 and the target (workpiece) 10 are installed in an environmental box, and laser processing can be performed in an environment in which the oxygen concentration is controlled to 0.5% or less.

[0033] Next, the steps for laser processing the heat dissipation section 20 according to this embodiment will be described with reference to the flow chart shown in Fig. 4. First, the target (workpiece) 10 is fixed on the fixed table 116, and then the position information required for processing is obtained by reading the alignment mark or the like, and the laser processing position is corrected, and processing preparation is completed.

[0034] In the flow chart of FIG. 4, first, in step S21, an instruction is issued to the stage control unit 119 to move the fixed table 116 to a desired position. Next, in step S22, the processing position data, the galvanometer mirror rest time, and the laser processing conditions are instructed to the galvanometer control unit 118. In step S23, the completion of the movement of the moving stage 117 is confirmed, and processing is started in step S24. In the processing step, first, in step S25, while the laser oscillation is stopped, the galvanometer mirror 113 is driven so that the laser is irradiated to the desired position when it is oscillated. Next, in step S26, the end of driving the galvanometer mirror 113 is confirmed, and then in step S27, the galvanometer mirror 113 is stopped for a preset time and made to wait. Next, in step S28, the laser is oscillated to process the second uneven structure 72. During processing, the target (workpiece) 10 is irradiated with the laser light emitted from the laser for a desired time or a desired number of pulses. Next, in step S29, it is confirmed that processing of one second recess 721 has been completed (see FIG. 2(b)), and laser oscillation is halted. Then, in step S30, it is determined whether processing of all areas that can be processed by the galvanometer mirror 113 has been completed. If not, the process returns to step S25 and processing continues. On the other hand, if processing of all areas that can be processed by the galvanometer mirror 113 has been completed, processing of the above-mentioned areas is deemed to be complete. If the heat dissipation section 20 can be manufactured by processing only the above-mentioned areas, the manufacturing process ends here, but if processing of other areas is required, the process returns to step S21.

[0035] In this embodiment, by using a laser processing machine, it is possible to form a concave-convex structure at a predetermined position on the surface of the target (workpiece) 10 while suppressing oxidation. Here, if a femtosecond laser is used as the laser oscillator 111, it is possible to perform laser processing on high-melting-point metals such as tungsten and molybdenum while suppressing oxidation. As described above, by irradiating the laser light for a desired time or number of pulses, the evaporated molecules of the evaporated target (workpiece) 10 aggregate in the gas phase, become particles, and adhere to the surface of the target (workpiece) 10. The adhered particles form an SWS, which can improve the emissivity of the target 10. As the SWS, it is preferable that the structure has a concave-convex structure with a pitch or distance between convex parts (distance between concave parts) less than 1 / 2 the peak wavelength of the electromagnetic wave that radiates heat, and a depth three times or more. With this structure, the change in the refractive index at the interface in the depth direction relative to the peak wavelength of the electromagnetic wave that radiates heat is made gentle, and the reflection of the electromagnetic wave can be effectively suppressed and the emissivity can be improved. Even if the function of the SWS of the first uneven structure 71 is insufficient, the emissivity can be improved by using it in combination with the second uneven structure 72. Furthermore, since oxidation of the processed surface can be suppressed, even when the temperature of the target 10 made of a high-melting point metal is raised to near its melting point, the loss of the microstructure due to melting caused by the drop in the melting point of the processed surface can be suppressed, and a decrease in emissivity can be prevented. In other words, the emissivity can be maintained even in a usage environment where the target becomes hot, and radiative cooling can be effectively utilized.

[0036] In this embodiment, the galvanometer mirror 113 is stopped intermittently to process the heat dissipation portion 20. However, the galvanometer mirror 113 may be kept stopped, and the laser light may be continuously scanned while blinking to perform processing.

[0037] The X-ray generating device 100 according to this embodiment can be used, for example, in an X-ray computed tomography (CT) device shown in Fig. 5. Fig. 5 is a cross-sectional view of an X-ray CT device 600. The X-ray CT device 600 includes a stator 200 and a rotor 150, and is configured such that the rotor 150 rotates with respect to the stator 200 around the Z-axis as the rotation axis.

[0038] The X-ray CT device 600 has a plate-shaped section 201, an X-ray irradiation section 202, an X-ray detection section 203, a signal amplification section 204, a cooling section 205, a power supply section 206, and a power supply control section 207. The plate-shaped section 201, the X-ray irradiation section 202, the X-ray detection section 203, the signal amplification section 204, the cooling section 205, the power supply section 206, and the power supply control section 207 are each components installed on the rotor 150.

[0039] The plate-shaped part 201 is an annular plate-shaped member installed inside the cylindrical rotor 150. At the center of the plate-shaped part 201, an imaging opening 208 is provided, into which a subject, such as a human or other living organism, which is the subject of the X-ray CT, is inserted.

[0040] The manner in which the subject is inserted into the imaging opening 208 is not particularly limited, but for example, a bed (not shown) on which the subject lies slides into the imaging opening 208 along the Z direction of the imaging opening 208, thereby inserting the subject into the imaging opening 208. Note that the subject is not necessarily limited to a living being such as a human being, and may be an article such as an industrial product.

[0041] The X-ray irradiation unit 202, the X-ray detection unit 203, the signal amplification unit 204, the cooling unit 205, the power supply unit 206, and the power supply control unit 207 are each attached to one surface in the Z direction of the plate-shaped unit 201. The X-ray irradiation unit 202, the X-ray detection unit 203, the signal amplification unit 204, the cooling unit 205, the power supply unit 206, and the power supply control unit 207 rotate about the Z axis as a rotation axis by the rotation of the plate-shaped unit 201 accompanying the rotation of the rotor 150 by the rotary drive device 10. Note that each of these units may be attached to one or the other surface or both surfaces of the plate-shaped unit 201 in the Z direction. Furthermore, each of these units may be disposed between a plurality of coil rows.

[0042] The X-ray irradiation unit 202 and the X-ray detection unit 203 are installed on the same plane in the Z direction of the plate-shaped unit 201. The X-ray irradiation unit 202 and the X-ray detection unit 203 are arranged in the diameter direction of the annular plate-shaped unit 201 so as to face each other across the Z axis, which is the axis of rotation of the plate-shaped unit 201.

[0043] The X-ray irradiation unit 202 is an irradiation unit that irradiates the subject with X-rays, which are radiation, while the rotor 150 makes one revolution around the subject. The X-ray irradiation unit 202 is, for example, the X-ray generator 100. The power supply unit 206 is a power supply device that supplies voltages for X-ray irradiation, such as tube voltage for the X-ray tube, to the X-ray irradiation unit 202. The power supply control unit 207 is a control device that controls the supply of tube voltage by the power supply unit 206. The cooling unit 205 is a cooling device that cools the X-ray irradiation unit 202, which generates heat when irradiating X-rays.

[0044] The X-ray detection unit 203 is a detector that detects X-rays that are irradiated from the X-ray irradiation unit 202 toward the subject and transmitted through the subject. The X-ray detection unit 203 outputs a detection signal corresponding to the detected X-rays. The signal amplification unit 204 amplifies the detection signal output from the X-ray detection unit 203. The signal amplification unit 204 outputs the amplified detection signal to a system control unit (not shown). The system control unit generates an X-ray CT image by image processing or the like based on the detection signal from the signal amplification unit 204.

[0045] <Second embodiment> The target 10 according to the second embodiment will be described with reference to Fig. 6. The heat dissipation section 20 in this embodiment differs from that in the first embodiment in that only the first uneven structure 71 is formed, and the second uneven structure 72 is not formed.

[0046] In this embodiment, Fig. 6 is an enlarged view of the area surrounded by circle C in Fig. 2(a). Even when the second uneven structure 72 is not provided, the heat dissipation performance can be improved by only the first uneven structure 71. The mechanism by which the heat dissipation performance is improved by the first uneven structure 71 is the same as that of the first embodiment.

[0047] The heat dissipation section 20 of this embodiment can be fabricated using the laser processing machine 110 shown in FIG. 3, as in the first embodiment. However, in this embodiment, instead of depositing molecules evaporated by laser light as in the first embodiment, the first uneven structure 71 is formed by processing the surface of the target (workpiece) to a desired depth with laser light. Therefore, for the first uneven structure 71 of this embodiment, the distance L1 between adjacent first convex portions or first concave portions can be set to a constant value like the pitch P1. In addition, the first uneven structure of this embodiment may be formed by lithography (dry etching using a mask) instead of laser processing. Furthermore, as a method for forming the first uneven structure, a method of depositing particles on the surface of the target (workpiece) by physical vapor deposition, chemical vapor deposition, or the like can also be used.

[0048] <Example> Next, the present invention will be described in more detail by showing targets formed under various processing conditions as examples and comparative examples, but the present invention is not limited to the following examples.

[0049] (Example 1-1) In Example 1-1, the surface of a member made of tungsten was processed using the laser processing machine 110 described with reference to FIG. 3. Nitrogen gas was supplied into the environmental box of the laser processing machine 110, and the member made of tungsten was placed in a nitrogen environment in which the oxygen concentration was maintained at 0.5% or less. The processing conditions were a laser wavelength of 1064 nm, a laser output of 4 W, a pulse width of 258 fs, and an oscillation frequency of 200 kHz, and a plurality of holes were formed on the surface of the member so that the pitch P2 of the convex or concave portions was 40 μm. The irradiation time per hole was 5000 μs. A second uneven structure 72 was formed by the series of these holes, and a first uneven structure 71 was formed by the accumulation of the member (particles) cut by the laser processing (see FIG. 2(b)). After the accumulation of the particles, a heat treatment was performed at 1100° C. in hydrogen to reduce the oxygen taken into the surface of the member, and the structure was stabilized in a high-temperature usage environment. By performing this treatment, a stable high emissivity can be obtained even in a high-temperature usage environment of 1000° C. or more. The heat treatment is preferably carried out at 800° C. or higher.

[0050] 7 and 8 are scanning electron microscope (SEM) photographs (drawing substitute photographs) showing the surface of a member made of tungsten before and after the heat treatment in this example. Fig. 7(a) is a magnified photograph of the surface of the member before the heat treatment, and Fig. 7(b) is a magnified photograph of the surface of the member after the heat treatment. As shown in Fig. 7, the recesses 721 of the second uneven structure 72 were arranged in a honeycomb pattern, and the depth of the recesses 721 was 70 μm.

[0051] Fig. 8(a) is an SEM photograph (a substitute for a drawing) of Fig. 7(a) enlarged, and Fig. 8(b) is an SEM photograph (a substitute for a drawing) of Fig. 7(b) enlarged. The first uneven structure 71 after the heat treatment had a structure in which particles were accumulated, and the distance L1 between adjacent first protrusions 710 varied from 110 nm to 580 nm. The average distance L1 was 360 nm. The emissivity after the heat treatment was 0.55.

[0052] (Example 1-2) In Example 1-2, the surface of the member was processed under the same conditions as in Example 1-1, except that a plurality of holes were formed on the surface of the member so that the pitch P2 of the convex or concave portions was 30 μm. The emissivity after the heat treatment was 0.86.

[0053] (Examples 1-3) In Example 1-3, the surface of the member was processed under the same conditions as in Example 1-2, except that the laser processing was performed in the atmosphere. The first uneven structure 71 after the heat treatment had a structure in which particles were accumulated, and the distance L1 between adjacent first protrusions 710 varied from 100 nm to 590 nm. The average distance L1 was 310 nm. The emissivity after the heat treatment was 0.65.

[0054] (Comparative Example) In the comparative example, the member made of tungsten was not subjected to surface processing, but was subjected to only heat treatment. Therefore, the member surface did not have the first and second uneven structures. The emissivity after heat treatment was 0.08.

[0055] (Evaluation Results) The processing conditions and emissivity of Examples 1-1 to 1-3 and Comparative Example are shown in Table 1. By providing holes of a desired size, the emissivity could be significantly improved. In particular, in Example 1-2, the emissivity could be improved more than in Example 1-1 by reducing the pitch P2 of the second uneven structure.

[0056] In Examples 1-1 and 1-2, the laser processing was performed in a nitrogen environment to reduce the oxygen concentration, but an inert gas such as argon or helium that does not react with the target material to lower the melting point or form a compound that has sublimation properties may also be used.

[0057] [Table 1]

[0058] Example 2 In this embodiment, the first uneven structure 71 was formed on the heat dissipation section 20 by dry etching. As shown in FIG. 9(a), gold nanoparticles 102 were applied onto a member 101 made of tungsten. Then, as shown in FIG. 9(b), Ar ions 103 generated and accelerated by an Ar ion source were irradiated, and the member 101 was dry etched using the nanoparticles 102 as a mask. After processing to a depth of 900 nm, the mask was removed as shown in FIG. 9(c), and the first uneven structure 71 with a pitch P1 of 300 nm was formed on the member 101, thereby manufacturing the heat dissipation section 20. The emissivity was 0.70.

[0059] By forming the first uneven structure 71 on the heat dissipation section 20 made of a high melting point metal, it is possible to prevent a decrease in emissivity even when the heat dissipation section 20 is heated to near its melting point. In other words, the emissivity can be maintained even in a high-temperature usage environment, and radiative cooling can be effectively utilized. Instead of the gold nanoparticles 102, an etching mask can also be formed using a photolithography process.

[0060] In the above-described embodiment, the target used in the X-ray generating device is given as the structure, but the structure of the present invention is not limited to this and can be applied to various articles. For example, in electronic devices such as PCs, it can be used as a means for releasing heat to the outside, such as in a housing surrounding electronic components. In addition, a structure may be formed by providing an uneven structure such as that of the present invention on the surface of a heat dissipation sheet. The above-described embodiment can be appropriately modified within the scope of the technical concept. In addition, multiple embodiments can be combined. In addition, some items of at least one embodiment can be deleted or replaced. Furthermore, new items can be added to at least one embodiment.

[0061] The disclosure of this specification includes not only what is explicitly described in this specification, but also all matters that can be understood from this specification and the drawings attached to this specification. The disclosure of this specification also includes the complement of each concept described in this specification. In other words, if this specification contains a statement that "A is greater than B," for example, this specification can be said to disclose that "A is not greater than B" even if the statement that "A is not greater than B" is omitted. This is because when it is stated that "A is greater than B," it is assumed that the case in which "A is not greater than B" is taken into consideration.

[0062] The disclosure of the present invention is given below.

[0063] (Configuration 1) A structure that is heated to 700°C or higher, the structure having a heat dissipation section that dissipates heat from the structure, the surface of the heat dissipation section having a first uneven structure in which a plurality of first convex sections and a plurality of first concave sections are alternately arranged, the peak wavelength of electromagnetic waves radiated from the heat dissipation section being 3 μm or less, and the distance between adjacent first convex sections of the plurality of first convex sections or the distance between adjacent first concave sections of the plurality of first concave sections being less than 1 / 2 of the peak wavelength.

[0064] (Configuration 2) The structure described in configuration 1, wherein the structure constitutes a target for an electron tube, the structure capable of serving as a heat source includes a portion of the target for an electron tube that is irradiated with electrons, and at least a portion of a surface of the target for an electron tube has the first uneven structure.

[0065] (Configuration 3) A structure that can be heated to 700°C or higher, the structure having a heat dissipation section that dissipates heat from the structure, the heat dissipation section having a first uneven structure on a surface thereof in which a plurality of first protrusions and a plurality of first recesses are alternately arranged, the structure constituting a target for an electron tube, the heat dissipation section including a portion that is irradiated with electrons from the target for an electron tube, the first uneven structure being formed on at least a portion of the surface of the target for an electron tube, and the distance between adjacent first protrusions of the plurality of first protrusions, or the distance between adjacent first recesses of the plurality of first recesses, is less than 1 / 2 of the peak wavelength of electromagnetic waves thermally radiated from the heat dissipation section.

[0066] (Configuration 4) 4. The structure according to any one of configurations 1 to 3, wherein the heat dissipation portion and the first uneven structure are made of a metal having a melting point of 1500° C. or higher.

[0067] (Configuration 5) 5. The structure described in any one of structures 1 to 4, wherein the nitrogen content in the first uneven structure at a depth of 100 nm or less from the surface is 1 at% or more, or the oxygen content is 10 at% or less.

[0068] (Configuration 6) The structure described in any one of configurations 1 to 5, characterized in that the surface of the heat dissipation portion has a second uneven structure in which a plurality of second convex portions and a plurality of second concave portions are alternately arranged, and the distance between adjacent second convex portions among the plurality of second convex portions is longer than the distance between the first convex portions, or the distance between adjacent second concave portions among the plurality of second concave portions is longer than the distance between the first concave portions, and the first uneven structure is provided on a surface of the second uneven structure.

[0069] (Configuration 7) The structure according to configuration 6, wherein the second uneven structure is made of a metal having a melting point of 1500° C. or higher.

[0070] (Configuration 8) The structure according to configuration 6 or 7, wherein the distance between the second convex portions or the distance between the second concave portions is 10 μm or more.

[0071] (Configuration 9) 9. The structure according to any one of configurations 1 to 8, wherein the distance between the first convex portions or the distance between the first concave portions is 50 nm or more.

[0072] (Configuration 10) 4. The structure according to claim 1 or 3, wherein the depth of the first uneven structure is 50 nm or more and less than 1500 nm.

[0073] (Configuration 11) 11. The structure according to any one of configurations 1 to 10, wherein the first uneven structure contains particles, and the particle size of the particles is 50 nm or more and less than 1500 nm.

[0074] (Configuration 12) 12. The structure of any one of configurations 1 to 11, wherein the first uneven structure contains particles, and the difference between the minimum particle size of the particles and the maximum particle size of the particles is 300 nm or more.

[0075] (Configuration 13) 4. The structure according to claim 2, wherein the heat dissipation portion is used in a vacuum.

[0076] (Configuration 14) 14. The structure according to claim 13, further comprising an electron emission source for irradiating the location with electrons.

[0077] (device 1) 15. An X-ray generating device comprising the structure according to configuration 14 and a container housing the structure therein.

[0078] (device 2) 2. The X-ray generating apparatus according to claim 1, further comprising a means for rotating the target for the electron tube.

[0079] (device 3) 3. An X-ray CT apparatus comprising: an X-ray generating apparatus according to claim 1 or 2; and a detection means for detecting X-rays irradiated from the X-ray generating apparatus.

[0080] (device 4) The X-ray CT device described in device 3 is characterized in that the X-ray generating device and the detection means face each other across a subject placed in the X-ray CT device, and the detection means detects X-rays that have passed through the subject among the X-rays irradiated from the X-ray generating device.

[0081] (Method 1) A method for manufacturing a heat dissipation part having a first uneven structure in which a plurality of first convex portions and a plurality of first concave portions are alternately arranged on a surface of a member, the method comprising: a processing step of cutting the surface of the member with laser light; and a depositing step of forming the first uneven structure by depositing a portion of the member cut in the processing step on the surface, wherein the distance between adjacent first convex portions among the plurality of first convex portions, or the distance between adjacent first concave portions among the plurality of first concave portions, is less than 1 / 2 of the peak wavelength of electromagnetic waves thermally radiated from the heat dissipation part.

[0082] (Method 2) The manufacturing method described in Method 1, characterized in that in the processing step, a second uneven structure is formed on the surface of the member in which a plurality of second convex portions and a plurality of second concave portions are alternately arranged, and the distance between adjacent second convex portions among the plurality of second convex portions is longer than the distance between the first convex portions, or the distance between adjacent second concave portions among the plurality of second concave portions is longer than the distance between the first concave portions, and the first uneven structure is provided on the surface of the second uneven structure.

[0083] (Method 3) 3. The manufacturing method according to method 1 or 2, characterized in that after the depositing step, the heat dissipation part is subjected to a heat treatment at 800° C. or more in a hydrogen atmosphere. [Explanation of symbols]

[0084] 20 Heat dissipation part 71 First uneven structure 710 First protrusion 711 First recess P1 Distance between adjacent first protrusions

Claims

1. A structure having a heat dissipation portion for dissipating heat, a first uneven structure in which first protrusions and first recesses are alternately arranged on a surface of the heat dissipation portion; The peak wavelength of the electromagnetic wave radiated from the heat dissipation portion is 3 μm or less, A structure characterized in that the distance between adjacent first convex portions among the multiple first convex portions of the first uneven structure, or the distance between adjacent first concave portions among the multiple first concave portions of the first uneven structure, is less than 1 / 2 of the peak wavelength.

2. The structure according to claim 1, characterized in that the structure constitutes a target for an electron tube, the heat dissipation portion includes a portion where electrons from the target for an electron tube are irradiated, and the first uneven structure is provided on at least a portion of a surface of the target for an electron tube.

3. The structure described in claim 1, characterized in that the first uneven structure is made of a metal having a melting point of 1500°C or higher.

4. 2. The structure according to claim 1, wherein a portion of the first uneven structure that is 100 nm or less deep from the surface has a nitrogen content of 1 at % or more, or an oxygen content of 10 at % or less.

5. a second uneven structure in which second protrusions and second recesses are alternately arranged on a surface of the heat dissipation portion; a distance between adjacent second convex portions of the second uneven structure is longer than a distance between the first convex portions, or a distance between adjacent second concave portions of the first uneven structure is longer than a distance between the first concave portions, The structure according to claim 1 , wherein the first uneven structure is provided on a surface of the second uneven structure.

6. The structure according to claim 5 , wherein the second uneven structure is made of a metal having a melting point of 1500° C. or higher.

7. 6. The structure according to claim 5, wherein the distance between the second convex portions or the distance between the second concave portions is 10 μm or more.

8. 2. The structure according to claim 1, wherein the distance between the first convex portions or the distance between the first concave portions is 50 nm or more.

9. The structure according to claim 1 , wherein the first uneven structure has a depth of 50 nm or more and less than 1500 nm.

10. The structure according to claim 1 , wherein the first uneven structure includes particles, and the particle size of the particles is 50 nm or more and less than 1500 nm.

11. The structure according to claim 1 , wherein the first uneven structure includes particles, and a difference between a minimum particle size of the particles and a maximum particle size of the particles is 300 nm or more.

12. The structure according to claim 2 , wherein the heat dissipation portion is used in a vacuum.

13. 13. The structure of claim 12, further comprising an electron emission source for irradiating the location with electrons.

14. An X-ray generating device comprising: the structure according to claim 13; and a container that houses the structure therein.

15. 15. An X-ray generating apparatus according to claim 14, further comprising a means for rotating the target for the electron tube.

16. 15. An X-ray CT apparatus comprising: an X-ray generating apparatus according to claim 14; and a detection means for detecting X-rays irradiated from said X-ray generating apparatus.

17. 17. The X-ray CT apparatus according to claim 16, wherein the X-ray generating device and the detecting means face each other across a subject placed in the X-ray CT apparatus, and the detecting means detects X-rays that have passed through the subject out of the X-rays irradiated from the X-ray generating device.

18. A method for manufacturing a heat dissipation part having a first uneven structure in which first protrusions and first recesses are alternately arranged on a surface of a member, the method comprising the steps of: a processing step of cutting the surface of the member with a laser beam; a depositing step of depositing a part of the member cut in the processing step on the surface to form the first uneven structure, a distance between adjacent first convex portions among the plurality of first convex portions of the first uneven structure, or a distance between adjacent first concave portions among the plurality of first concave portions, is less than 1 / 2 of a peak wavelength of an electromagnetic wave thermally radiated from the heat dissipation portion.

19. In the processing step, a second uneven structure in which second convex portions and second concave portions are alternately arranged is formed on the surface of the member, a distance between adjacent second convex portions of the second uneven structure is longer than a distance between the first convex portions, or a distance between adjacent second concave portions of the second uneven structure is longer than a distance between the first concave portions, The manufacturing method according to claim 18 , wherein the first uneven structure is provided on a surface of the second uneven structure.

20. 20. The method according to claim 18, further comprising the step of: subjecting the heat dissipation portion to a heat treatment at 800[deg.] C. or more in a hydrogen atmosphere after the depositing step.

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