X-ray generating device

Abstract

An X-ray generating apparatus includes: an X-ray tube having an electron gun for generating an electron beam, a target for generating X-rays by impacting the electron beam, and a vacuum housing for housing the electron gun and the target; and a control unit for controlling the driving of the X-ray tube, the control unit executing: an actual use mode that makes the irradiation range of the electron beam on the target a desired irradiation range; and a preheating mode executed before the actual use mode, wherein the density of electrons impacting the target increases from the start time of the preheating mode to the start time of the actual use mode.

Description

Technical Field

[0001] This disclosure relates to an X-ray generating apparatus. Background Technology

[0002] Japanese Patent Application Publication No. 2007-149601 discloses an X-ray generating device, which consists of two electron guns and two targets, forming a microfocus by the electron guns and targets, and heating the anode using the electron guns and targets. Summary of the Invention

[0003] The problem the invention aims to solve

[0004] In microfocus X-ray sources, X-rays need to be output with a reduced focal depth, resulting in localized high temperatures near the focal point in the target material. The heating and cooling cycles caused by the electron beam generate thermal stress within the target, potentially leading to cracking or other damage. If the target cracks and detaches, or its surface shape changes, it will be impossible to output X-rays properly.

[0005] This disclosure is made to solve the above-mentioned problems, and the purpose is to provide an X-ray generating device that can suppress target cracking.

[0006] Technical means for solving problems

[0007] The gist of this disclosure is as follows.

[0008] [1] An X-ray generating apparatus comprising: an X-ray tube having an electron gun for generating an electron beam, a target for generating X-rays by impacting the electron beam, and a vacuum housing housing the electron gun and the target; and a control unit for controlling the driving of the X-ray tube, the control unit executing: an actual use mode that makes the irradiation range of the electron beam on the target a desired irradiation range; and a preheating mode executed before the actual use mode, wherein the density of electrons impacting the target increases from the start time of the preheating mode to the start time of the actual use mode.

[0009] In this X-ray generating apparatus, the density of electrons impacting the target increases from the start of the preheating mode to the start of the actual use mode. That is, the electron density in the preheating mode is lower than that in the actual use mode. According to this structure, compared to the case where the actual use mode is executed from the beginning without a preheating mode, a sharp rise in temperature near the irradiation range of the target can be suppressed in the actual use mode. Therefore, stress accumulation caused by the temperature difference between the irradiation range and its periphery in the actual use mode can be reduced. From the above, it can be seen that this X-ray generating apparatus can suppress target cracking.

[0010] [2] The X-ray generating apparatus as described in [1] further comprises: an electron gun power supply unit for supplying power to the electron gun; a target support unit for supporting the target; and a high-voltage power supply unit for supplying high voltage to the target support unit. The control unit controls the electron gun power supply unit so that the intersection point, which is the convergence point of the electron beam, is located between the electron gun and the target, and controls the high-voltage power supply unit so that the tube current of the X-ray tube in the preheating mode is the same as the tube current of the X-ray tube in the actual use mode. In the X-ray generating apparatus, the energy of the electron beam irradiating the target that is not converted into X-rays is converted into heat, and the target and the target support unit expand due to this heat. In the structure where the intersection point is located between the electron gun and the target, due to the expansion of the target and the target support unit, the irradiation range of the electron beam on the target continuously narrows from the start of the preheating mode to the start of the actual use mode. As a result, compared to performing the actual use mode from the beginning without performing the preheating mode, the temperature difference between the irradiation area and its periphery in the actual use mode can be reduced. Therefore, stress accumulation caused by the temperature difference between the irradiation area and its periphery in the actual use mode can be reliably reduced. Furthermore, since the tube current of the X-ray tube is the same in both the preheating mode and the actual use mode, the execution of the preheating mode and the actual use mode can be simplified.

[0011] [3] In the X-ray generating apparatus described in [2], the control unit controls the electron gun power supply unit to make the convergence angle of the electron beam 0.1° or more and 120° or less. In this case, the difference between the irradiation range of the electron beam at the beginning of the preheating mode and the irradiation range of the electron beam at the beginning of the actual use mode can be increased. Therefore, stress accumulation caused by the temperature difference between the irradiation range and its periphery in the actual use mode can be reduced more reliably.

[0012] [4] In the X-ray generating apparatus as described in [2] or [3], the size of the irradiation range at the start time of the preheating mode is more than 1.1 times and less than 2.0 times the size of the irradiation range at the start time of the actual use mode. In this case, stress accumulation due to the temperature difference between the irradiation range and its periphery in the actual use mode can be reduced more reliably.

[0013] [5] In any one of [2] to [4], the size of the irradiation range at the start time of the actual use mode is 5 μm or more and 500 μm or less. In this case, X-rays can be generated appropriately.

[0014] [6] In any one of [2] to [5], the control unit controls the high-voltage power supply unit so that the tube current of the X-ray tube in the preheating mode is the same as the tube current of the X-ray tube in the actual use mode, which is between 50 μA and 1 mA. In this case, X-rays can be generated appropriately.

[0015] [7] The X-ray generating apparatus as described in [1] further comprises: an electron gun power supply unit for supplying power to the electron gun; a target support unit for supporting the target; and a high-voltage power supply unit for supplying high voltage to the target support unit. The control unit controls the electron gun power supply unit so that the intersection point, which is the convergence point of the electron beam, is located inside the target in the irradiation direction of the electron beam, and controls the high-voltage power supply unit so that the tube current of the X-ray tube in the preheating mode is less than the tube current of the X-ray tube in the actual use mode. In the structure in which the intersection point is located inside the target in the irradiation direction of the electron beam, due to the expansion of the target and the target support unit, the irradiation range of the electron beam continuously expands from the start of the preheating mode to the start of the actual use mode. Furthermore, since the tube current in the preheating mode is less than the tube current in the actual use mode, it is possible to reliably achieve an increase in the density of electrons impacting the target from the start of the preheating mode to the start of the actual use mode while suppressing a sharp rise in temperature near the irradiation range of the target.

[0016] [8] In the X-ray generating apparatus as described in [7], the size of the irradiation range at the start time of the preheating mode is more than 0.5 times and less than 0.9 times the size of the irradiation range at the start time of the actual use mode. In this case, stress accumulation due to the temperature difference between the irradiation range and its periphery in the actual use mode can be reduced more reliably.

[0017] [9] In the X-ray generating apparatus as described in [7] or [8], the size of the irradiation range at the start time of the actual use mode is 5 μm or more and 500 μm or less. In this case, X-rays can be appropriately generated.

[0018] According to this disclosure, it is possible to suppress target material cracking. Attached Figure Description

[0019] Figure 1 This is a cross-sectional view of an X-ray generating apparatus according to one embodiment of the present disclosure.

[0020] Figure 2 This is a diagram illustrating the problem in the comparative example.

[0021] Figure 3This is a diagram illustrating the problem in the comparative example.

[0022] Figure 4 This is a diagram illustrating the problem in the comparative example.

[0023] Figure 5 This is a diagram illustrating the problem in the comparative example.

[0024] Figure 6 This is a schematic diagram illustrating an example of the relationship between the location of the intersection point and the irradiation range of the electron beam.

[0025] Figure 7 (a) is a schematic diagram illustrating an example of the electron beam irradiation range at the start of the preheating mode. Figure 7 (b) is a schematic diagram of an example of the irradiation range of the electron beam at the start of an actual use mode.

[0026] Figure 8 Figure (a) is an example of a diagram showing the change in the size of the electron beam irradiation range in the preheating mode and the actual use mode. Figure 8 Figure (b) is an example of the variation in tube current between preheating mode and actual use mode. Figure 8 (c) is a graph showing an example of the change in power density as the density of electrons in the impact target.

[0027] Figure 9 This is another schematic diagram illustrating the relationship between the location of the intersection point and the irradiation range of the electron beam.

[0028] Figure 10 (a) is a schematic diagram showing another example of the electron beam irradiation range at the start of the preheating mode. Figure 10 (b) is a schematic diagram of another example of the irradiation range of the electron beam at the start of the actual use mode.

[0029] Figure 11 Figure (a) is another example illustrating the change in the size of the electron beam irradiation range in the preheating mode and the actual use mode. Figure 11 Figure (b) is another example illustrating the variation in tube current between preheating mode and actual usage mode. Figure 11 (c) is another example of the power density variation representing the density of electrons as a bombarding target. Detailed Implementation

[0030] Hereinafter, a preferred embodiment of an X-ray generating apparatus according to one aspect of the present disclosure will be described in detail with reference to the accompanying drawings. Furthermore, terms such as "upper" and "lower," indicating a defined direction, are used only for convenience based on the states shown in the drawings.

[0031] Figure 1 This is a cross-sectional view of an X-ray generating apparatus according to one embodiment of the present disclosure. Figure 1 The X-ray generating apparatus 1 shown includes an X-ray tube 2, a housing 3, a first insulating part 4, a power supply part 5, a conductive component 6, and a conductive coating 8. The X-ray generating apparatus 1 is, for example, a microfocus X-ray source used for X-ray nondestructive testing.

[0032] X-ray tube 2 is a vacuum tube used to generate X-rays. X-ray tube 2 includes a housing 21 (vacuum housing), an electron gun 22, a target 23, and an anode 24. Housing 21 houses the electron gun 22, target 23, and anode 24. The space inside housing 21 is a vacuum-evacuated space. Housing 21 has a head 211, a tube body 212, and a flange 213. The head 211 is formed into a bottomed cylindrical shape from a metal material such as stainless steel. The tube body 212 is formed into a bottomed cylindrical shape from an insulating material such as glass. The head 211 is hermetically joined to the tube body 212 in a manner that allows communication between the interior of the head 211 and the interior of the tube body 212. The flange 213 is formed into an annular shape from a metal material such as stainless steel along the outer edge of the head 211. Here, the direction along the central axis (tube axis) A1 of the tube body 212 is called the Z-axis direction, the direction perpendicular to the Z-axis direction is called the X-axis direction, and the direction perpendicular to both the Z-axis and X-axis directions is called the Y-axis direction.

[0033] The electron gun 22 generates an electron beam within the housing 21 and emits the electron beam toward the target 23. The shape of the electron beam can be, for example, approximately circular, elliptical, or polygonal. Here, the shape of the electron beam refers to the shape of the irradiation range of the electron beam toward the target 23 (e.g., the irradiation range at half-width at half-height). The electron gun 22 is composed of a hot cathode that emits thermionic electrons, an anode that accelerates the electrons, and an electron lens (not shown) that adjusts the focusing of the electron beam. The electron gun 22 is fixed to the head 211 such that its central axis A2 is orthogonal to the central axis A1 of the tube body 212. The central axis A2 of the electron gun 22 is along the X-axis.

[0034] The target 23 is housed within the casing 21 and generates X-rays by being struck by an electron beam emitted from the electron gun 22. The target 23 is formed into a plate shape from a high-melting-point metal material such as tungsten. The target 23 is supported within the casing 21 by an anode 24 in a manner opposite to the electron gun 22 in the X-axis direction.

[0035] The anode 24 applies the voltage generated by the power supply unit 5 to the target 23. Therefore, the anode 24 and the target 23 are electrically connected. The anode 24 is formed from a metallic material such as copper and is a rod extending along the Z-axis. The anode 24 extends from outside the housing 21 to inside the housing 21 with its central axis aligned with the central axis A1 of the tube body 212. The anode 24 is fixed to the bottom of the tube body 212. The front end face of the anode 24 inside the housing 21 is an inclined surface relative to both the central axes A1 and A2. The target 23 is embedded in the front end 24a of the anode 24, flush with the front end face of the anode 24.

[0036] The housing 3 houses a portion of the X-ray tube 2. In the X-ray generating apparatus 1 of the first embodiment, the housing 3 houses the tube body 212. The housing 3 is formed into a bottomed cylindrical shape from a metal material such as aluminum. The housing 3 has an upper part 31 and a side part 32. The side part 32 is formed into a cylindrical shape with the Z-axis as the height direction. The upper part 31 blocks one end of the side part 32 in the Z-axis direction (the upper end in this embodiment). An opening 31a is provided in the upper part 31. The X-ray tube 2 is located inside the opening 31a. The flange 213 is fixed to the upper part 31 with the tube body 212 inside the housing 3. The other end of the side part 32 in the Z-axis direction (the lower end in this embodiment) is fixed to the upper end of the power supply part 5 (the upper surface 51b of the second insulating part 51). The first insulating part 4 is sealed inside the housing 3.

[0037] The first insulating part 4 electrically insulates the X-ray tube 2 from other components. The first insulating part 4 is a liquid insulating part. The first insulating part 4 is an insulating oil with, for example, mineral oil or ester oil as its main component. The first insulating part 4 covers the tube body 212, the portion of the anode 24 that protrudes outside the housing 21, and the portion of the conductive component 6 that protrudes outside the second insulating part 51 within the housing part 3. In this embodiment, the interior of the housing part 3 is filled with the first insulating part 4.

[0038] The power supply unit 5 generates a voltage to be applied to the target material 23 via the conductive member 6 and the anode 24. The power supply unit 5 is disposed on one side (the lower side of the housing 21) in the Z-axis direction relative to the housing 21. The power supply unit 5 is parallel to the X-ray tube 2 along the Z-axis direction. The power supply unit 5 has a second insulating part 51 and a circuit part 52 (high voltage power supply part).

[0039] The second insulating part 51 is a solid insulating part that electrically insulates the circuit part 52 from other components. The second insulating part 51 is formed into a cuboid shape from a resin material such as epoxy resin. The surface 51a of the second insulating part 51 is composed of an upper surface 51b, which is the side of the housing 21, a lower surface 51c, which is the opposite side of the upper surface 51b, and a side surface 51d that connects the upper surface 51b and the lower surface 51c to each other. A portion of the upper surface 51b is formed into a raised shape. This portion is in contact with the first insulating part 4 inside the housing part 3. A conductive coating 8 is applied to the side surface 51d of the second insulating part 51, and the potential of the side surface 51d is set to the ground potential.

[0040] The circuit section 52 has a substrate 521 that is a rectangular printed circuit board. The surface of the substrate 521 is orthogonal to the Y-axis direction. A first voltage section 52a, a boost section 52b, and a second voltage section 52c are mounted on the surface of the substrate 521. The first voltage section 52a is an input terminal for receiving a first voltage from the outside and is electrically connected to the boost section 52b. The boost section 52b boosts the first voltage to a second voltage. The boost section 52b is, for example, a Crocroft-Walton circuit. The second voltage section 52c is an output terminal for outputting a second voltage to the target 23 via the conductive member 6 and the anode 24, and is electrically connected to the boost section 52b.

[0041] The boost unit 52b is located at the central portion of the surface of the substrate 521. The first voltage unit 52a is located on one side of the Z-axis (lower surface 51c side) relative to the boost unit 52b. The second voltage unit 52c is located on the other side of the Z-axis (upper surface 51b side) relative to the boost unit 52b.

[0042] The circuit section 52 is embedded in the second insulating section 51 in such a way that the entire circuit section 52 is located within the second insulating section 51. The circuit section 52 is embedded in the second insulating section 51 in such a way that the substrate 521 extends straight along the Z-axis direction.

[0043] The conductive component 6 electrically connects the second voltage section 52c to the target material 23 via the anode 24. Therefore, the conductive component 6 is conductive. The conductive component 6 and the anode 24 form a target support section 60 supporting the target material 23 at one end. In the following description, the conductive component 6 and the anode 24 may be collectively referred to as the target support section 60. The circuit section 52 (high-voltage power supply section) is connected to the other end of the target support section 60 formed by the conductive component 6 and the anode 24, and supplies a high voltage to the target support section 60.

[0044] The conductive component 6 is formed into a rod shape from a metal material such as aluminum. One end of the conductive component 6 (the other end) is electrically connected to the second voltage section 52c, and the other end of the conductive component 6 is electrically connected to the base end 24b of the anode 24 (the portion of the anode 24 located outside the housing 21). The conductive component 6 is embedded in the second insulating section 51 such that a portion of the conductive component 6 is located within the second insulating section 51. The remaining portion of the conductive component 6 protrudes outside the second insulating section 51. The portion of the conductive component 6 that protrudes outside the second insulating section 51 is electrically connected to the base end 24b of the anode 24 inside the housing section 3.

[0045] The X-ray generating device 1 also includes an electron gun power supply unit 116 and a control unit 117.

[0046] The electron gun power supply unit 116 is a voltage generating circuit that generates the voltage applied to the electron gun 22, and is a structure that supplies power to the electron gun 22. The electron gun power supply unit 116 is controlled by the control unit 117. The electron gun power supply unit 116 can be mounted together with the circuit unit 52 inside the second insulating part 51, or it can be mounted on a circuit board outside the second insulating part 51. The control unit 117 controls the driving of the X-ray tube 2. In this embodiment, the control unit 117 controls the driving of the X-ray tube 2 by controlling the electron gun power supply unit 116 and the circuit unit 52. The control unit 117 is mounted on a circuit board outside the second insulating part 51.

[0047] The control unit 117 is physically composed of a processor such as a CPU, and storage media such as RAM and ROM. The control unit 117 can be a smartphone or tablet terminal integrated with the display unit and the input unit, or it can be composed of a microcomputer or FPGA (Field-Programmable Gate Array).

[0048] Next, in the X-ray generating apparatus 1 of this embodiment, the variation of the power density d, which is the density of electrons impacting the target 23, will be explained while comparing it with a comparative example. When the electron beam shape is approximately circular, the power density d is the value obtained by dividing the X-ray output, i.e., the power input to the target 23, by the focal diameter (diameter) of the electron beam. When the electron beam shape is elliptical, the power density d is the value obtained by dividing the X-ray output by the square root of the product of the major and minor axes of the ellipse. When the electron beam shape is polygonal, the power density d is the value obtained by dividing the X-ray output by the average of the diameters of the circumcircle and incircle of the polygon.

[0049] In the comparative example, from the start of electron beam irradiation, the electron beam is controlled so that the irradiation range (focal size) of the electron beam on the target 23 is the desired irradiation range. Furthermore, after X-ray emission begins, the power density d of the electrons striking the target 23 remains constant. The power density d is, for example, approximately 1.0 W / μm, and is set to a constant high state. Additionally, the "tube voltage - tube current" of the X-ray tube is, for example, set to approximately "200 kV - 800 μA", and the "focal diameter of the electron beam" is, for example, set to "100 μm". Here, the X-ray output is represented by the product of the tube voltage (kV) and the tube current (mA). In this case, the X-ray output is 160 W, which, when divided by the electron beam focal diameter, is 1.6 W / μm; the X-ray output is set to a constant high output. In this comparative example, from the start of X-ray emission, the electron beam is irradiated with the desired irradiation range on the target 23, maintaining a relatively high power density d and a relatively high X-ray output. Furthermore, a higher tube voltage results in a higher energy electron beam irradiating the target 23, and a larger tube current results in a greater total amount of electron beam irradiating the target 23.

[0050] Figures 2-5 This is a diagram illustrating the problem in the comparative example. Figure 2 (a) represents the irradiation state of the target 23 by the electron beam in the X-ray tube 2. Figure 2 (b) indicates Figure 2 A magnified view of a portion (target 23) in (a). Figure 2 (c) represents Figure 2 A magnified view of a portion of (b) (the irradiation range of the electron beam in target 23). As shown... Figure 2 As shown in (b), the electron beam irradiation of the target 23 resulted in a damaged region DA in the target 23. More specifically, as... Figure 2 As shown in (c), crack C, which causes target cracking, is generated around the damaged area DA. With a constant power density d, if a relatively high-output electron beam is irradiated onto the target 23 with a desired irradiation range from the start of irradiation, the irradiated area within the target 23 locally becomes hot, resulting in stress accumulation due to the temperature difference between the irradiated area and its surroundings. The higher the X-ray output, the greater the heat received by the target 23 and the target support 60 due to electron beam irradiation. The greater the received heat, the thermal expansion of the target 23 and the target support 60 before reaching thermal equilibrium occurs simultaneously with the evaporation of the target 23 caused by heat concentration, which easily leads to uneven changes in the surface shape of the target 23. The heating and cooling thermal cycle caused by the electron beam further promotes the aforementioned stress accumulation, thereby generating crack C, which causes target cracking. Furthermore, as... Figure 2As shown in (c), the damaged area DA becomes elongated, and the change in the surface shape of the target 23 within the irradiation range of the electron beam also becomes a problem.

[0051] Reference Figures 3-5 The reason why the damaged area DA in the comparative example becomes longitudinally elongated is explained. For example... Figure 3 As shown, if a relatively high-output electron beam irradiates the target 23, the surface of the target 23 is eroded due to evaporation within the irradiation range of the electron beam, resulting in a rough surface with depressions. Furthermore, of the energy of the electron beam irradiating the target 23, the portion not converted into X-rays is converted into heat, thereby heating the target 23 and the target support 60. This heat causes the target support 60 to expand and elongate. Due to the elongation T1, the irradiation range gradually moves from the initial position IP to the stable position SP. The stable position SP is the irradiation range of the electron beam in the target 23 when the target support 60 is in thermal equilibrium. Because the surface of the target 23 is continuously eroded within the irradiation range of the electron beam during the continuous elongation of the target support 60 due to thermal expansion, as... Figure 4 As shown, with the continuous change of the irradiation range from the initial position IP to the stable position SP, a damage region DA with an elongated, concave shape is formed. When the electron beam irradiates the region containing the damage region DA, X-rays are generated due to the scattering of electrons within the concave area of ​​the damage region DA, thus generating X-rays over a wider range than the irradiation range of the electron beam. That is, although the focal diameter of the electron beam (the irradiation conditions of the electron beam) remains unchanged, the surface shape of the target material 23 changes within the irradiation range of the electron beam, resulting in a larger X-ray generation area in the target material 23. In other words, the focal size of the X-rays extracted from the X-ray generating device 1 becomes larger. Figure 5 (a) shows the focal size of the approximately circular X-ray emitted from X-ray generator 1, as shown in the figure. Figure 5 As shown in (b), it will change into an elongated shape. Such unintentional enlargement of the apparent X-ray focal size can lead to blurred X-ray images, etc.

[0052] As explained above, in a structure like the comparative example, where the electron beam irradiation range is made to the desired irradiation range from the start of X-ray emission, and the power density d is kept constant at a relatively high level, problems arise such as crack C causing target material cracking, and changes in the X-ray focus size (changes in X-ray focus shape) causing X-ray image blurring.

[0053] As a structure to solve such problems, in the X-ray generating apparatus 1 of this embodiment, an actual use mode and a preheating mode performed before the actual use mode are set. From time t0, which is the start time of the preheating mode, to time t1, which is the start time of the actual use mode, the power density d increases. Here, for example, time t0 is the time when X-rays begin to be emitted, and time t1 is the time when the target 23 and the target support 60 reach thermal equilibrium.

[0054] In this embodiment, in order to increase the power density d from time t0 to time t1, control is performed on the crossover point CP, which is the point where the electron beam converges, and on the tube current. Hereinafter, refer to... Figure 6 , Figure 7 and Figure 8 The control of the crossover point CP and the control of the tube current in this embodiment will be explained in further detail.

[0055] First, the control of the intersection point (CP) will be explained. Figure 6 This is a schematic diagram illustrating an example of the relationship between the location of the intersection point and the irradiation range of the electron beam. In this embodiment, as... Figure 6 As shown, the control unit 117 controls the electron gun power supply unit 116 to position the crosspoint CP between the electron gun 22 and the target 23. This arrangement, where the crosspoint CP is located near the front of the target 23, the object of electron beam irradiation, is also referred to as overfocus. That is, in this embodiment, it can also be said that the control unit 117 controls the electron gun power supply unit 116 to make the electron beam overfocused relative to the target 23. In this case, the focal diameter of the electron beam can be set to the same focal diameter in both the preheating mode and the actual use mode. That is, in this embodiment, the focal diameter of the electron beam does not need to be controlled after electron beam irradiation begins. In one example, the focal diameter of the electron beam can be set to the same focal diameter between 5 μm and 500 μm in both the preheating mode and the actual use mode.

[0056] In cases of over-focusing, a portion of T1 is generated due to the elongation of the target support 60, causing a change in the electron beam irradiation range. This change in the electron beam irradiation range is as follows: Figure 6 and Figure 7 As shown. Figure 7 (a) is a schematic diagram showing the irradiation range of the electron beam at the start of the preheating mode. Figure 7 (b) is a schematic diagram showing the irradiation range of the electron beam at the start of the actual usage mode. Figure 6 and Figure 7In the example shown, the irradiation range of the electron beam at time t0, which is the start time of the preheating mode, is illustrated as irradiation range 101, and the irradiation range of the electron beam at time t1, which is the start time of the actual use mode, is illustrated as irradiation range 201. Figure 7 As shown, the irradiation range 101 and the irradiation range 201 are, for example, circular in shape. In this case, the size of the irradiation range 101 is represented by the size Rs1, which is the diameter of the circle, and the size of the irradiation range 201 is represented by the size Rf1. In this embodiment, the size Rf1 is the diameter of the circle.

[0057] In the case of overfocusing, the irradiation range 101 is at its maximum at time t0, after which the irradiation range of the electron beam continuously narrows. Furthermore, the shrinking of the irradiation range of the electron beam stops at time t1, after which the irradiation range 201 becomes approximately constant. In other words, the diameter of the electron beam becomes constant at dimension Rf1. Thus, in the case of overfocusing, as part T1 continuously elongates, the irradiation range of the electron beam shrinks from irradiation range 101 to irradiation range 201.

[0058] In this embodiment, the irradiation range 201 can be the desired irradiation range in the X-ray generating apparatus 1. As described above, since the irradiation range of the electron beam continuously shrinks between time t0 and time t1, the irradiation range 101 becomes a larger range than the desired irradiation range when the irradiation range 201 is the desired irradiation range. Therefore, in the case of over-focusing, the control unit 117 can control the electron gun power supply unit 116 to make the irradiation range of the electron beam at the start of the preheating mode larger than the desired irradiation range.

[0059] As the irradiation range of the electron beam changes, the size of that irradiation range also changes. This change in the size of the irradiation range of the electron beam is similar to... Figure 6 and Figure 7 As shown. Similar to the irradiation range of the electron beam, in the case of over-focusing, the size Rs1 is largest at time t0, which is the start time of the preheating mode, and thereafter the size of the irradiation range continuously decreases. Furthermore, at time t1, which is the moment when the target 23 and the target support 60 reach thermal equilibrium, the decrease of the above-mentioned size stops, and thereafter the size becomes approximately constant at the size Rf1. As described above, in this embodiment, since the irradiation range 201 is the desired irradiation range in the X-ray generating apparatus 1, the size Rf1, as its size, is the size of the desired irradiation range.

[0060] In one example, the size Rs1 can be 5 μm or more and 1000 μm or less. The size Rf1 can be 5 μm or more and 500 μm or less. The size Rs1 can be 1.1 times or more and 2.0 times the size Rf1. In this embodiment, since the size Rs1 is 130 μm and the size Rf1 is 100 μm, the size Rs1 is 1.3 times the size Rf1.

[0061] return Figure 6 In this embodiment, the control unit 117 can control the electron gun power supply unit 116 to make the convergence angle θ of the electron beam 0.1° or more and 120° or less. The convergence angle θ is an angle representing, for example, the expansion of the trajectory BT of the electron beam when it converges toward the intersection point CP. The convergence angle θ is also an indicator of the change in the size of the irradiation range of the electron beam from time t0 to time t1. For example, the larger the convergence angle θ, the larger the change in the size of the irradiation range of the electron beam, that is, the greater the difference between size Rs1 and size Rf1. In the X-ray generating apparatus 1, by setting the convergence angle θ within the above range, the difference between size Rs1 and size Rf1 can be clearly defined.

[0062] Next, the control of the tube current will be explained. In this embodiment, the control unit 117 controls the circuit unit 52 to make the tube current of the X-ray tube 2 in the preheating mode the same as the tube current of the X-ray tube 2 in the actual use mode. Here, "same" does not mean that only the index value must be identical. Regarding the tube current of the X-ray tube 2 in the preheating mode and the tube current of the X-ray tube 2 in the actual use mode being the same, even if the value contains a small difference within a preset range, it can be considered as "same". In one example, the control unit 117 can control the circuit unit 52 to make the tube current of the X-ray tube 2 in the preheating mode the same as the tube current of the X-ray tube 2 in the actual use mode at the tube current E1. The tube current E1 can be, for example, 50μA or more and 1mA or less.

[0063] The above-mentioned electron beam irradiation range and the relationship between tube current and power density d are as follows: Figure 8 As shown. Figure 8 (a) is a figure illustrating an example of the variation in the size of the electron beam irradiation range in the preheating mode and the actual use mode. Figure 8 (b) is a diagram illustrating an example of the change in tube current in preheating mode and actual use mode. Figure 8 (c) is a graph representing an example of the change in power density d, which is the density of electrons as a bombarding target. Figure 8 The vertical axis of (a) represents the size of the electron beam irradiation range [μm]. Figure 8 The vertical axis of (b) represents the tube current [μA]. Figure 8The vertical axis of (c) represents the power density d [W / μm]. Figure 8 The horizontal axis of (a), (b) and (c) represents time [min].

[0064] In this embodiment, such as Figure 8 As shown in (a) and (b), the size of the electron beam irradiation range decreases from Rs1 at time t0 to Rf1 at time t1, and the tube current E1 becomes the same after time t0. That is, in this embodiment, the irradiation range of the electron beam on the target 23 continuously narrows, while the total number of electrons impacting the target 23 remains unchanged. Therefore, as Figure 8 As shown in (c), the power density d increases from time t0 to time t1. Figure 8 In the example shown in (c), the power density d exhibits power density ds1 at time t0, and then increases continuously until time t1. Furthermore, the power density d exhibits power density df1 at time t1, and then becomes approximately constant.

[0065] In one example, the power density ds1 can be 0.5 W / μm or more and 2 W / μm or less. The power density df1 can be 1 W / μm or more and 3 W / μm or less. In this example, the control unit 117 can control the electron gun power supply unit 116 and the circuit unit 52 to make the power density ds1 0.5 W / μm or more and 2 W / μm or less. The control unit 117 can control the electron gun power supply unit 116 and the circuit unit 52 to make the power density df1 1 W / μm or more and 3 W / μm or less.

[0066] As explained above, in the X-ray generating apparatus 1, the power density d, which is the density of electrons impacting the target 23, increases from time t0, the start time of the preheating mode, to time t1, the start time of the actual use mode. That is, in the X-ray generating apparatus, the power density d in the preheating mode becomes lower than the power density d in the actual use mode. According to this structure, compared to the case where the actual use mode is executed from the beginning without performing the preheating mode, a sharp rise in temperature near the irradiation range of the target can be suppressed in the actual use mode. Therefore, stress accumulation caused by the temperature difference between the irradiation range and its periphery in the actual use mode can be reduced. From the above, it can be seen that the X-ray generating apparatus can suppress target cracking.

[0067] Furthermore, in the X-ray generating apparatus 1, the electron beam is controlled at time t1 to make the irradiation range 201 of the electron beam on the target 23 the desired irradiation range. As a result, the problem of X-ray focus size variation that exists when the electron beam is irradiated onto the target 23 from the beginning with the desired irradiation range, caused by focus movement that occurs with the etching of the target 23 (caused by the irradiation range movement due to the expansion of the target 23 and the target support 60 due to thermal expansion), can be suppressed.

[0068] In the X-ray generating apparatus 1, the control unit 117 controls the electron gun power supply unit 116 to position the crossover point CP between the electron gun 22 and the target 23, and controls the circuit unit 52 to make the tube current of the X-ray tube 2 in the preheating mode the same as the tube current of the X-ray tube 2 in the actual use mode. In this case, due to the expansion of the target 23 and the target support 60, the irradiation range of the electron beam on the target 23 continuously narrows from time t0 to time t1. As a result, compared with the case where the actual use mode is executed from the beginning without executing the preheating mode, the temperature difference between the irradiation range and its periphery in the actual use mode can be reduced. Therefore, stress accumulation caused by the temperature difference between the irradiation range and its periphery in the actual use mode can be reliably reduced. Furthermore, since the tube current of the X-ray tube 2 is the same in both the preheating mode and the actual use mode, the execution of the preheating mode and the actual use mode can be carried out easily.

[0069] In the X-ray generating apparatus 1, the control unit 117 controls the electron gun power supply unit 116 to make the convergence angle θ of the electron beam 0.1° or more and 120° or less. In this case, the difference between the irradiation range 101 of the electron beam at time t0 and the irradiation range 201 of the electron beam at time t1 can be increased. Therefore, stress accumulation caused by the temperature difference between the irradiation range and its periphery in actual use mode can be reduced more reliably.

[0070] In the X-ray generating apparatus 1, the size Rs1 of the irradiation range 101 at time t0 is more than 1.1 times and less than 2.0 times the size Rf1 of the irradiation range 201 at time t1. In this case, stress accumulation caused by the temperature difference between the irradiation range and its periphery in actual use mode can be reduced more reliably.

[0071] In the X-ray generating apparatus 1, the size Rf1 of the irradiation range 201 at time t1 is 5 μm or more and 500 μm or less. Under this condition, X-rays can be generated appropriately.

[0072] In the X-ray generating apparatus 1, the control unit 117 controls the circuit unit 52 to ensure that the tube current of the X-ray tube 2 in the preheating mode is the same as that in the actual use mode, between 50 μA and 1 mA. Under these conditions, X-rays can be generated appropriately.

[0073] The embodiments of this disclosure have been described above, but this disclosure is not necessarily limited to the above embodiments, and various changes can be made without departing from its spirit.

[0074] In this variation, in order to increase the power density d from time t0 to time t1, control is also performed on the crossover point CP and the tube current. See below for further details. Figure 9 , Figure 10 and Figure 11 The control of the crossover point CP and the control of the tube current in this variant will be explained in further detail.

[0075] First, the control of the intersection point (CP) will be explained. Figure 9 This is a schematic diagram illustrating another example of the relationship between the location of the intersection point and the irradiation range of the electron beam. In this modified example, as... Figure 9 As shown, the control unit 117 controls the electron gun power supply unit 116 to position the crosspoint CP inside the target 23 in the electron beam irradiation direction. This arrangement, where the crosspoint CP is located inside the target 23, the object of electron beam irradiation, is also referred to as underfocus. That is, in this embodiment, it can also be said that the control unit 117 controls the electron gun power supply unit 116 to make the electron beam underfocused relative to the target 23. In this case, the focal diameter of the electron beam can be set to the same in both the preheating mode and the actual use mode. That is, in this modified example, the focal diameter of the electron beam may not be controlled after the electron beam irradiation begins.

[0076] Even in the case of underfocus, the electron beam irradiation range changes due to a partial T1 caused by the elongation of the target support 60. This change in the electron beam irradiation range, such as... Figure 9 and Figure 10 As shown. Figure 10 (a) is a schematic diagram of another example of the irradiation range of the electron beam at the start of the preheating mode. Figure 10 (b) is a schematic diagram illustrating another example of the electron beam irradiation range at the start of an actual usage mode. Figure 9 and Figure 10 In the example shown, the irradiation range of the electron beam at time t0, which is the start time of the preheating mode, is illustrated as irradiation range 102, and the irradiation range of the electron beam at time t1, which is the start time of the actual use mode, is illustrated as irradiation range 202. Figure 10 As shown, the irradiation range 102 and the irradiation range 202 are, for example, circular in shape. In this case, the dimensions Rs2 of the irradiation range 102 and Rf2 of the irradiation range 202 are, for example, represented by the diameter of the circle.

[0077] In the case of underfocus, the illumination range 102 is narrowest at time t0, and thereafter the illumination range of the electron beam continuously expands. Furthermore, the expansion of the illumination range of the electron beam stops at time t1, and thereafter the illumination range of the electron beam becomes approximately constant at illumination range 202. Thus, in the case of underfocus, as part of T1 continuously elongates, the illumination range of the electron beam expands from illumination range 102 to illumination range 202.

[0078] In this modified example, the irradiation range 202 is the desired irradiation range in the X-ray generating apparatus 1. As described above, between time t0 and time t1, the irradiation range of the electron beam continuously expands. Therefore, when the irradiation range 202 is the desired irradiation range, the irradiation range 102 becomes a range smaller than the desired irradiation range. Thus, in the case of underfocus, the control unit 117 can control the electron gun power supply unit 116 to make the irradiation range 102 of the electron beam at time t0 smaller than the desired irradiation range.

[0079] In this variation, as the irradiation range of the electron beam changes, the size of that irradiation range also changes. This change in the size of the irradiation range of the electron beam is also as... Figure 9 and Figure 10 As shown. Similar to the irradiation range of the electron beam, in the case of underfocus, the size Rs2 is smallest at time t0, and thereafter the size of the irradiation range continuously increases. Furthermore, the increase of the size stops at time t1, and thereafter the size becomes approximately constant at size Rf2. As described above, in this modified example, since the irradiation range 202 is the desired irradiation range in the X-ray generating apparatus 1, the size Rf2, as its size, is the size of the desired irradiation range.

[0080] In one example, the size Rs2 can be 5 μm or more and 300 μm or less. The size Rf2 can be 5 μm or more and 500 μm or less. The size Rs2 can be 0.5 times or more and 0.9 times the size Rf2. In this modified example, since the size Rs2 is 70 μm and the size Rf2 is 100 μm, the size Rs2 is 0.7 times the size Rf2.

[0081] Next, the control of the tube current will be explained. In this modified example, the control unit 117 controls the circuit unit 52 to make the tube current of the X-ray tube 2 in the preheating mode less than the tube current of the X-ray tube 2 in the actual use mode. In one example, the control unit 117 can control the circuit unit 52 to make the tube current of the X-ray tube 2 increase from time t0 to time t1. In this case, the tube current Es2, which is the tube current of the X-ray tube 2 at time t0, can be, for example, 0 μA or more and 100 μA or less. The tube current Ef2, which is the tube current of the X-ray tube 2 at time t1, can be, for example, 100 μA or more and 1 mA or less.

[0082] The above-mentioned electron beam irradiation range and the relationship between tube current and power density d are as follows: Figure 11 As shown. Figure 11 (a) is another example of the variation in the size of the electron beam irradiation range in the preheating mode and the actual use mode. Figure 11 (b) is another example of the variation in tube current in preheating mode and actual use mode. Figure 11 (c) is another example of the variation in power density d, which represents the density of electrons as a bombarding target. Figure 11 The vertical axis of (a) represents the size of the electron beam irradiation range [μm]. Figure 11 The vertical axis of (b) represents the tube current [μA]. Figure 11 The vertical axis of (c) represents the power density d. Figure 11 The horizontal axis of (a), (b) and (c) represents time [min].

[0083] In this variation, such as Figure 11 As shown in (a) and (b), the size of the electron beam irradiation range increases from Rs2 at time t0 to Rf2 at time t1, and the tube current also increases from the tube current Es2 at time t0 to the tube current Ef2 at time t1. That is, in this embodiment, while the irradiation range of the electron beam on the target 23 continuously expands, the total number of electrons impacting the target 23 continuously increases. Therefore, as Figure 11 As shown in (c), the power density d increases from time t0 to time t1. Figure 11 In the example shown in (c), the power density d exhibits power density ds2 at time t0 and increases continuously until time t1. Furthermore, the power density d exhibits power density df2 at time t1 and then becomes approximately constant. The range of power density ds2 can be the same as the range of power density ds1, and the range of power density df2 can also be the same as the range of power density df1.

[0084] In this modified example, the control unit 117 controls the electron gun power supply unit 116 to position the crosspoint CP inside the target 23 in the electron beam irradiation direction, and controls the circuit unit 52 to make the tube current of the X-ray tube 2 in the preheating mode less than the tube current of the X-ray tube 2 in the actual use mode. In this modified example, due to the expansion of the target 23 and the target support 60, the irradiation range of the electron beam continuously expands from time t0 to time t1. Furthermore, since the tube current in the preheating mode is less than the tube current in the actual use mode, it is possible to reliably achieve a structure in which the power density d increases from time t0 to time t1 while suppressing a sharp rise in temperature near the irradiation range of the target.

[0085] In this modified example, the size Rs2 of the irradiation range 102 at time t0 is more than 0.5 times and less than 0.9 times the size Rf2 of the irradiation range 202 at time t1. In this case, stress accumulation caused by the temperature difference between the irradiation range and its periphery in actual use mode can be reduced more reliably.

[0086] In this modified example, the size Rf2 of the irradiation range 202 at time t1 is 5 μm or more and 500 μm or less. Under this condition, X-rays can be appropriately generated.

Claims

1. An X-ray generating device, comprising: An X-ray tube comprising an electron gun for generating an electron beam, a target material for generating X-rays by impacting the electron beam, and a vacuum housing for housing the electron gun and the target material; and The control unit controls the driving of the X-ray tube. The control unit executes: an actual use mode that makes the irradiation range of the electron beam on the target material the desired irradiation range; and a preheating mode executed before the actual use mode. From the start of the preheating mode to the start of the actual use mode, the density of electrons impacting the target increases.

2. The X-ray generating apparatus as described in claim 1, further comprising: An electron gun power supply unit that supplies power to the electron gun; The target support portion that supports the target material; and A high-voltage power supply unit that supplies high voltage to the target support portion. The control unit controls the electron gun power supply unit so that the intersection point, which is the convergence point of the electron beam, is located between the electron gun and the target material, and controls the high-voltage power supply unit so that the tube current of the X-ray tube in the preheating mode is the same as the tube current of the X-ray tube in the actual use mode.

3. The X-ray generating apparatus as described in claim 2, wherein, The control unit controls the electron gun power supply unit to make the convergence angle of the electron beam 0.1° or more and 120° or less.

4. The X-ray generating apparatus as described in claim 2 or 3, wherein, The size of the irradiation range at the start time of the preheating mode is more than 1.1 times and less than 2.0 times the size of the irradiation range at the start time of the actual use mode.

5. The X-ray generating apparatus according to any one of claims 2 to 4, wherein, The size of the irradiation range at the start time of the actual use mode is greater than 5 μm and less than 500 μm.

6. The X-ray generating apparatus according to any one of claims 2 to 5, wherein, The control unit controls the high-voltage power supply unit so that the tube current of the X-ray tube in the preheating mode is the same as the tube current of the X-ray tube in the actual use mode, which is between 50μA and 1mA.

7. The X-ray generating apparatus as claimed in claim 1, further comprising: An electron gun power supply unit that supplies power to the electron gun; The target support portion that supports the target material; and A high-voltage power supply unit that supplies high voltage to the target support portion. The control unit controls the electron gun power supply unit so that the intersection point, which is the convergence point of the electron beam, is located inside the target material in the irradiation direction of the electron beam, and controls the high voltage power supply unit so that the tube current of the X-ray tube in the preheating mode is less than the tube current of the X-ray tube in the actual use mode.

8. The X-ray generating apparatus as claimed in claim 7, wherein, The size of the irradiation range at the start time of the preheating mode is more than 0.5 times and less than 0.9 times the size of the irradiation range at the start time of the actual use mode.

9. The X-ray generating apparatus as claimed in claim 7 or 8, wherein, The size of the irradiation range at the start time of the actual use mode is greater than 5 μm and less than 500 μm.

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