X-ray generating device

Abstract

An X-ray generating apparatus includes a housing, an electron gun having an electron emission portion that emits electrons within the housing, a target that generates X-rays by the electrons incident thereto within the housing, a window member that seals an opening of the housing and transmits the X-rays, a tube voltage application portion that applies a tube voltage between the electron emission portion and the target, and a magnetic field formation portion that causes the electrons to be deflected by forming a magnetic field between the electron emission portion and the target. The target has a thickness distribution, and is disposed such that, when the tube voltage is relatively high, the electrons are incident to a relatively thin portion of the thickness of the target when the tube voltage is relatively low.

Description

Technical Field

[0001] This invention relates to an X-ray generating device. Background Technology

[0002] Patent Document 1 describes a transmission-type X-ray tube device. The device includes: a vacuum perimeter that constitutes an X-ray tube; an X-ray transmission window disposed at one end of the vacuum perimeter; a metal thin film that forms an X-ray target disposed on the vacuum side of the X-ray transmission window; and an electron gun that generates an electron beam that irradiates the X-ray target.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2001-126650 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In the device described in Patent Document 1, the thickness of the metal thin film varies depending on the location, and a deflection electrode is provided to deflect the electron beam. The deflection electrode is composed of a pair of electrode plates arranged opposite each other between the target and the focusing electrode. Thus, in this device, the deflection voltage applied to the deflection electrode is varied according to the change in the accelerating voltage of the electron beam generated from the electron gun, thereby aiming to achieve a location with an appropriate film thickness for the electron beam to be incident on the target.

[0008] Thus, in the aforementioned technical field, it is required that the electron beam be incident on a target at an appropriate thickness according to its accelerating voltage. However, in the device described in Patent Document 1, in addition to controlling the accelerating voltage of the electron beam, it is also necessary to adjust the bias voltage in a manner corresponding to the accelerating voltage, which complicates the overall control.

[0009] Therefore, the object of the present invention is to provide an X-ray generating apparatus that avoids control complications and directs the electron beam to an appropriate position on the target.

[0010] Technical means to solve the problem

[0011] The X-ray generating apparatus of the present invention comprises: a housing; an electron gun having an electron emitting section that emits electrons within the housing; a target that generates X-rays by incident electrons within the housing; a window member that seals the opening of the housing and allows X-rays to pass through; a tube voltage applying section that applies a tube voltage between the electron emitting section and the target; and a magnetic field forming section for deflecting electrons by forming a magnetic field between the electron emitting section and the target; the target has a thickness distribution, and the target is arranged such that when the tube voltage is relatively high, electrons are incident on a relatively thin portion of the target's thickness when the tube voltage is relatively low.

[0012] In this device, a tube voltage is applied between the electron emission section of the electron gun and the target via a tube voltage application unit, and a magnetic field is formed between the electron emission section and the target via a magnetic field forming unit. Therefore, even if the magnetic field formed by the magnetic field forming unit is fixed (e.g., in time), if the acceleration and velocity of the electrons are varied by adjusting the tube voltage to a desired value, the radius of the electron's circular motion caused by the Lorentz force also changes. Consequently, the electron deflection vector caused by the magnetic field also changes automatically. For example, when the tube voltage is relatively high and the electrons move at high speed, the radius of the electron's circular motion caused by the Lorentz force increases, resulting in a smaller electron deflection vector. Conversely, when the tube voltage is relatively low and the electrons move at low speed, the radius of the electron's circular motion caused by the Lorentz force decreases, resulting in a larger electron deflection vector. Thus, in this device, the electron deflection vector is automatically adjusted in a manner corresponding to the desired tube voltage without controlling the formation (magnitude) of the magnetic field caused by the magnetic field generating unit. Therefore, by configuring a target with a thickness distribution such that electrons are incident on a relatively thin portion of the target when the tube voltage is relatively low, when the tube voltage is relatively high, the complexity of control can be (automatically) avoided and the electrons can be incident on the appropriate position of the target.

[0013] In the X-ray generating apparatus of the present invention, the target thickness may also be thinned from the center to the periphery, and the target may be arranged such that electrons are incident on the periphery side as the tube voltage relatively decreases. In this case, it is easy to form the target with the thickness distribution described above.

[0014] In the X-ray generating apparatus of the present invention, the magnetic field forming unit may also include a permanent magnet. In this way, in the apparatus, a fixed magnetic field can be formed simply by using a permanent magnet, reliably avoiding the complexity of control.

[0015] In the X-ray generating apparatus of the present invention, the window member may have a first surface opposite to the interior of the housing and a second surface on the interior side of the housing, with the target formed on the second surface. In this case, a so-called transmission-type X-ray generating apparatus is constituted.

[0016] In the X-ray generating apparatus of the present invention, the target may also be supported in a tilted position relative to both the electron gun and the window member. In this case, a so-called reflective X-ray generating apparatus is constituted.

[0017] The effects of the invention

[0018] According to the present invention, an X-ray generating apparatus is provided that can avoid the complexity of control and direct the electron beam to the appropriate position of the target. Attached Figure Description

[0019] Figure 1 This is a block diagram of an X-ray generating apparatus according to one embodiment.

[0020] Figure 2 yes Figure 1 The cross-sectional view of the X-ray tube is shown.

[0021] Figure 3 It is a schematic diagram used to illustrate the relationship between the electron beam and the target.

[0022] Figure 4 It is Figure 2 A partial enlarged schematic side view.

[0023] Figure 5 This is a cross-sectional view of a modified X-ray tube.

[0024] Figure 6 It is Figure 5 A partial enlarged schematic side view. Detailed Implementation

[0025] Hereinafter, an embodiment will be described in detail with reference to the accompanying drawings. Furthermore, in each drawing, the same or equivalent parts are labeled with the same symbols, and repeated descriptions are omitted.

[0026] [Structure of X-ray generating device]

[0027] like Figure 1 As shown, the X-ray generating apparatus 10 includes an X-ray tube 1 and a power supply unit 11. The X-ray tube 1 and the power supply unit 11 are supported within a metal housing (not shown). As an example, the X-ray tube 1 is a small-focus X-ray source, and the X-ray generating apparatus 10 is a device used in X-ray non-destructive examination for magnifying and observing the internal structure of an object under inspection.

[0028] like Figure 2 As shown, the X-ray tube 1 includes a housing 2, an electron gun 3, a target 4, and a window component 5. The X-ray tube 1 is configured as a sealed, transparent X-ray tube that does not require replacement of parts, etc., as described below.

[0029] The housing 2 has a head 21 and a vacuum tube 22. The head 21 is formed of metal in a bottomed cylindrical shape. The vacuum tube 22 is formed of an insulating material such as glass in a bottomed cylindrical shape. The opening 22a of the vacuum tube 22 is hermetically sealed with the opening 21a of the head 21. In the X-ray tube 1, the centerline of the housing 2 is called the tube axis A. An opening 23 is formed on the bottom wall 21b of the head 21. The opening 23 is located on the tube axis A. When viewed from a direction parallel to the tube axis A, the opening 23 appears, for example, as a circle with the tube axis A as its centerline.

[0030] Electron gun 3 emits an electron beam B within housing 2. Electron gun 3 includes a heater 31, a cathode 32, a first gate electrode 33, and a second gate electrode 34. The heater 31, cathode 32, first gate electrode 33, and second gate electrode 34 are sequentially arranged on tube axis A from the bottom wall 22b side of vacuum tube 22. As an example, the axis A3 of electron gun 3 (refer to…) Figure 4 The axis A3 of the electron gun 3 is aligned with the tube axis. Alternatively, the axis A3 of the electron gun 3 can be defined as, for example, the central axis of the electron gun 3 (e.g., the central axis of the cathode 32, the first gate electrode 33, and the second gate electrode 34), or it can be defined as the trajectory of the electron beam B without deflecting it as described below. The heater 31 is composed of a filament and heats up when energized. The cathode 32 is heated by the heater 31 to release electrons. That is, the cathode 32 is the electron emission section that emits electrons within the housing 2.

[0031] The first gate electrode 33 is cylindrical to adjust the amount of electrons released from the cathode 32. Additionally, the first gate electrode 33 also serves as an extraction electrode for drawing out electrons emitted from the cathode 32. The initial velocity of the electrons is determined by the voltage applied to the first gate electrode 33 (extraction voltage). The second gate electrode 34 is cylindrical to focus electrons passing through the first gate electrode 33 onto the target 4. The heater 31, cathode 32, first gate electrode 33, and second gate electrode 34 are each electrically and physically connected to a plurality of lead pins 35 penetrating the bottom wall 22b of the vacuum tube 22. The lead pins 35 are each electrically connected to the power supply section 11 of the X-ray generating apparatus 10.

[0032] Window member 5 seals the opening 23 of housing 2. Window member 5 is formed into a plate shape from a material with high X-ray permeability, such as diamond or beryllium. Window member 5 is, for example, a circular plate centered on tube axis A. Window member 5 has a first surface 51 and a second surface 52. The first surface 51 is the surface opposite to the interior of housing 2, and the second surface 52 is the surface on the interior side of housing 2. The first surface 51 and the second surface 52 are, for example, flat surfaces perpendicular to tube axis A. Target 4 is formed on the second surface 52 of window member 5. Target 4 is, for example, formed into a film shape from tungsten. Target 4 generates X-rays R within housing 2 through the incident electron beam B. In this embodiment, the X-rays R generated in target 4 pass through target 4 and window member 5 and exit to the outside.

[0033] The window member 5 is mounted on the mounting surface 24 around the opening 23 of the housing 2. The mounting surface 24 is, for example, a flat surface perpendicular to the tube axis A, formed in the head 21. The window member 5 can be hermetically joined to the mounting surface 24 via a bonding member (not shown) such as brazing material. In the X-ray tube 1, the target 4 is electrically connected to the head 21, and the target 4 and the window member 5 are thermally connected to the head 21. As an example, the target 4 is grounded via the head 21. Thus, a tube voltage is applied between the cathode 32 of the electron gun 3 and the target 4.

[0034] The tube voltage defines the acceleration of electrons emitted from the cathode 32 toward the target 4. In the X-ray generating apparatus 10, a negative voltage is supplied to the cathode 32 via the lead pin 35 through the power supply unit 11, and the target 4 (anode) is set to ground potential, thus applying a tube voltage between the cathode 32 and the target 4. In this way, the power supply unit 11, the cathode 32, and the target 4 cooperate to form a tube voltage application unit that applies the tube voltage. On the other hand, the power supply unit 11 is also connected to the first gate electrode 33, which serves as the lead-out electrode, and a lead-out voltage is applied to the first gate electrode 33. Therefore, the power supply unit 11 constitutes a lead-out voltage application unit. In addition, as an example, the heat generated in the target 4 by the incident electron beam B is directly or via the window member 5 transferred to the head 21, and further dissipated from the head 21 to the heat dissipation unit (not shown). In this embodiment, the internal space of the housing 2 is maintained at a high vacuum level by means of the housing 2, the target 4, and the window member 5.

[0035] In the X-ray generating apparatus 10 configured as described above, a negative voltage, based on the potential of the target 4, is applied to the electron gun 3 by the power supply unit 11. As an example, when the target 4 is at ground potential, the power supply unit 11 applies a negative high voltage (e.g., -10kV to -500kV) to each part of the electron gun 3 via each lead pin 35. The electron beam B emitted from the electron gun 3 is focused onto the target 4 along the tube axis A. The X-ray R generated in the irradiation area of ​​the electron beam B in the target 4 is focused on that irradiation area and passes through the target 4 and the window member 5 to the outside.

[0036] Here, the X-ray tube 1 has a deflection section 6. The deflection section 6 has a permanent magnet 61. The permanent magnet 61 is, for example, made of ferrite magnet, neodymium magnet, samarium cobalt magnet, AlNiCo alloy magnet, etc.

[0037] A permanent magnet 61 is disposed on the outside of the housing 2, for example, fixed to the flange of the head 21 via a fixing part (not shown). Thus, the permanent magnet 61 is mounted on the outside of the housing 2. Specifically, the permanent magnet 61 is disposed between the cathode 32 and the target 4 when viewed from a direction intersecting the tube axis A. As a result, a magnetic field is formed between the cathode 32 and the target 4, containing at least a component perpendicular to the direction of electron travel. In this way, the permanent magnet 61 functions as a magnetic field forming part for deflecting electrons by forming a magnetic field between the cathode 32 and the target 4.

[0038] Such a deflection section 6 deflects the electron beam B through the magnetic field formed by the permanent magnet 61, thus changing the incident position of the electron beam B on the target 4. When viewed radially from a direction perpendicular to the path of the electron beam B emitted from the cathode 32 towards the target 4, the deflection section 6 may include a portion overlapping that path. This allows the magnetic field formed by the permanent magnet 61 to appropriately act on the electron beam B. In this example, when viewed radially, the entire deflection section 6 is arranged to encompass the path of the electron beam B. Furthermore, the deflection section 6 is only required to form a magnetic field that deflects the electron beam B; it is not limited to being arranged in a manner that includes a portion overlapping the path of the electron beam B when viewed radially. For example, in... Figure 2 In this configuration, if the X-ray R emission direction is set to the upper side along the tube axis A and the opposite side is set to the lower side, the deflector 6 can also be positioned lower than the bottom wall 22b of the vacuum tube 22. The deflector 6 can also be rotatable around the tube axis A. In this case, the position of the electron beam B incident on the target 4 can be adjusted by rotating the deflector 6.

[0039] [Target Structure]

[0040] Next, when explaining the target structure, the relationship between the electron beam and the target will be discussed. In X-ray generating devices, since the energy of the X-rays generated varies depending on the tube voltage, the tube voltage may vary within a range such as 40kV to 130kV. Figure 3 As shown, the penetration depth of electron beam B1 into target 4A when accelerated with a relatively high tube voltage is greater than that of electron beam B2 when accelerated with a relatively low tube voltage.

[0041] Therefore, as Figure 3 As shown in (a), when the target 4A is relatively thick, the electron beam B1 at high tube voltage penetrates the target 4A to near the boundary between the target 4A and the support 5A (which here corresponds to the window member 5) (the deepest part of the target 4A). That is, the penetration depth is appropriate relative to the thickness of the target 4A. In other words, since the thickness of the target 4A that the X-rays generated in the target 4A need to pass through to reach the support 5A is small, the reduction in X-ray output caused by self-absorption due to the target 4A is suppressed. On the other hand, since the penetration depth of the electron beam B2 at low tube voltage remains near the surface of the target 4A, the thickness of the target 4A that the X-rays generated in the target 4A need to pass through to reach the support 5A is large, and there is a concern about the reduction in X-ray output caused by self-absorption due to the target 4A.

[0042] Furthermore, since most of the energy of electron beam B is converted into heat, there is a concern that target 4A may be damaged by heat if it is stored within target 4A. Therefore, like electron beam B1, it penetrates into target 4A in a manner that reaches near the boundary between target 4A and support 5A, thereby easily transferring the generated heat to support 5A and suppressing thermal damage to target 4A. On the other hand, since the penetration depth of electron beam B2 at low tube voltage remains near the surface of target 4A, it is not easy to transfer the generated heat to support 5A, raising concerns about thermal damage to target 4A. Thus, it can be said that electron beam B1 at high tube voltage is preferred when target 4A is relatively thick, but not preferred for electron beam B2 at low tube voltage. In addition, in order to effectively dissipate the heat generated inside target 4A, support 5A can be formed of a material with good thermal conductivity, such as diamond.

[0043] In addition, such as Figure 3 As shown in (b), when target 4B is relatively thin, even at a low tube voltage, electron beam B2 penetrates target 4B to near the boundary between target 4B and support 5A (the deepest part of target 4A). That is, the penetration depth is appropriate relative to the thickness of target 4B. On the other hand, since electron beam B1 at a high tube voltage passes through target 4B, it... Figure 3 Compared to case (a), the X-ray output is reduced.

[0044] In contrast, such as Figure 3 As shown in (c), consider constructing the target 4C with a non-uniform thickness. That is, consider creating a thickness distribution in the target 4C. Therefore, if the electron beam B1 at a high tube voltage is incident on a relatively thick position of the target 4C, and the electron beam B2 at a low tube voltage is incident on a relatively thin position of the target 4C, then in either electron beam, it can penetrate the target 4C to the vicinity of the boundary between the target 4C and the support 5A. Therefore, the reduction in X-ray output can be suppressed over a wide range of tube voltages, and thermal damage to the target 4C can be suppressed.

[0045] Therefore, as Figure 4 As shown, in the X-ray generating apparatus 10, the thickness T4 of the target 4 has a predetermined distribution. That is, the thickness T4 of the target 4 is distributed in a manner that varies according to its position in the plane intersecting the centerline of the electron gun 3, i.e., the axis A3 (tube axis A). The distribution is arbitrary, but in the example shown, when viewed from the direction intersecting the axis A3, the thickness T4 of the target 4 thins from the central portion 4a to the peripheral portion 4b.

[0046] Furthermore, in the X-ray generating apparatus 10, the electron beams B1 and B2 are appropriately positioned relative to the incident positions of the electron beams B1 and B2 on the target 4. Specifically, the target 4 is positioned such that electron beam B1, at a high tube voltage, is incident on a relatively thick portion of the target 4, and electron beam B2, at a low tube voltage, is incident on a relatively thick portion of the target 4. In other words, in the X-ray generating apparatus 10, the target 4 is positioned such that, compared to a relatively high tube voltage, electrons (electron beam B) are incident on a relatively thin portion of the target 4's thickness when the tube voltage is relatively low. Additionally, in Figure 4 In the diagram, the components including the first gate electrode 33 and the second gate electrode 34 of the electron gun 3 are omitted from the display.

[0047] The target 4, which has the thickness distribution described above, can be manufactured, for example, as follows: When forming the target 4 on the support (here, the window member 5) by film deposition, a mask corresponding to the periphery of the target 4 is used. The portion of the support that overlaps with the mask has a poor view from the evaporation source, thus hindering film deposition, and is deposited thinner than the central portion that does not overlap with the mask. Therefore, the target 4 can be manufactured with a thicker central portion and a thinner periphery. The difference in thickness (aspect ratio) between the central and peripheral portions can be controlled by factors such as the placement of the mask or the thickness of the mask plate.

[0048] [Functions and Effects]

[0049] In the X-ray generating apparatus 10, a tube voltage is applied between the cathode 32 and the target 4 of the electron gun 3 via the tube voltage application unit (power supply unit 11), and a magnetic field is formed between the cathode 32 and the target 4 via the permanent magnet 61 of the deflection unit 6. Therefore, if the acceleration and velocity of the electrons are changed by adjusting the tube voltage to a desired value, the radius of the circular motion of the electrons caused by the Lorentz force changes, and the deflection vector of the electrons caused by the magnetic field also changes automatically.

[0050] For example, when the tube voltage is relatively high and electrons move at high speeds, the radius of the circular motion of electrons caused by the Lorentz force increases, resulting in a smaller electron deflection vector. Conversely, when the tube voltage is relatively low and electrons move at low speeds, the radius of the circular motion of electrons caused by the Lorentz force decreases, resulting in a larger electron deflection vector. Thus, the X-ray generating device 10 automatically adjusts the electron deflection vector in a manner corresponding to the desired tube voltage, without controlling the formation (magnitude) of the magnetic field caused by the permanent magnet 61. Therefore, by configuring the target 4, which has a thickness distribution, such that electrons are incident on a relatively thin portion of the target when the tube voltage is relatively low compared to when it is relatively high, the complexity of control can be (automatically) avoided, and electrons can be incident on the appropriate position of the target 4.

[0051] Furthermore, as an example of the optimal value for the thickness T4 of the target 4 at the electron incident position, it is approximately 2 μm when the tube voltage is around 40 kV, and approximately 10 μm when the tube voltage is around 130 kV. Therefore, the target 4 can be formed with a thickness T4 distributed in the range of 2 μm to 10 μm.

[0052] Furthermore, in the X-ray generating apparatus 10, the thickness T4 of the target 4 decreases from the central portion 4a to the peripheral portion 4b, and the target 4 is arranged such that electrons are incident on the peripheral portion 4b side as the tube voltage relatively decreases. Therefore, it is easy to form the target 4 with the thickness T4 distributed as described above.

[0053] Furthermore, in the X-ray generating apparatus 10, a permanent magnet 61 is included as a magnetic field forming unit, which is installed in the housing 2 between the cathode 32 and the target 4. Therefore, in the X-ray generating apparatus 10, as long as a fixed magnetic field is formed by the permanent magnet 61, the complexity of control can be reliably avoided.

[0054] Furthermore, in the X-ray generating apparatus 10, the window member 5 has a first surface 51 on the side opposite to the interior of the housing 2 and a second surface 52 on the interior side of the housing 2, and the target 4 is formed on the second surface 52. Thus, a so-called transmission-type X-ray generating apparatus 10 is constituted.

[0055] [Variation Example]

[0056] The present invention is not limited to the embodiments described above. The X-ray tube 1 and the X-ray generating device 10 can also be configured as a sealed reflective type. For example... Figure 5 As shown, the main difference between the sealed reflective X-ray tube 1 and the sealed transmissive X-ray tube 1 described above is that the electron gun 3 is disposed within the housing 7 on the side of the head 21; and the target 4 is supported by a support member 8 instead of a window member 5. The housing 7 has a side tube 71 and a column 72. The side tube 71 is engaged with the side wall of the head 21 such that one opening 71a of the side tube 71 faces the interior of the head 21. The column 72 seals the other opening 71b of the side tube 71.

[0057] The heater 31, cathode 32, first gate electrode 33, and second gate electrode 34 are sequentially arranged in the side tube 71 starting from the column 72 side. Multiple lead pins 35 penetrate the column 72. The support member 8 penetrates the bottom wall 22b of the vacuum tube 22. The target 4 is fixed to the front end 81 of the support member 8 in a tilted position relative to both the electron gun 3 and the window member 5 on the tube axis A.

[0058] In this example, the deflecting part 6 is provided relative to the side tube 71 of the receiving part 7. Thus, the permanent magnet 61 is positioned between the cathode 32 and the target 4 via the holding member 62. As a result, a magnetic field is formed between the cathode 32 and the target 4, containing at least a component perpendicular to the direction of electron travel. In this way, the permanent magnet 61 also functions as a magnetic field forming part for deflecting electrons by forming a magnetic field between the cathode 32 and the target 4.

[0059] More specifically, such as Figure 6 As shown, the permanent magnet 61 is disposed outside the side tube 71 of the receiving section 7. Therefore, electrons emitted from the cathode 32 are deflected by the magnetic field generated by the permanent magnet 61, at least within the side tube 71. Furthermore, in Figure 6 In the diagram, the components including the first gate electrode 33 and the second gate electrode 34 of the electron gun 3 are omitted from the display.

[0060] In addition, the target 4 is the same as in the above embodiment, with a thickness T4 distribution, and is arranged such that when the tube voltage is relatively low, electrons (electron beam B) are incident on the relatively thin portion.

[0061] In an X-ray generating apparatus 10 equipped with a sealed reflective X-ray tube 1 as described above, as an example, with the head 21 and side tube 71 set to ground potential, a positive voltage is applied to the target 4 via the support member 8 by the power supply unit 11, and a negative voltage is applied to each part of the electron gun 3 via multiple lead pins 35 by the power supply unit 11. The electron beam B emitted from the electron gun 3 is focused onto the target 4 in a direction perpendicular to the tube axis A. The X-ray R generated in the irradiation area of ​​the electron beam B in the target 4 is focused on that irradiation area and emitted to the outside through the window member 5. Furthermore, when X-rays are generated by electrons incident on the target 4, since most of the incident energy is converted into heat, there is a concern that the target 4 may be damaged by heat if it is stored in the target 4. As a heat dissipation measure, a material with good thermal conductivity, such as copper, is used for the support member 8, and a material with high thermal conductivity, such as diamond, is also used for the support body 5A. Furthermore, in order to efficiently transfer the heat generated inside the target 4 from the support 5A to the support member 8, the electron beam B penetrates the target 4A near the boundary between the target 4A and the support 5A. This facilitates the transfer of heat to the support 5A and suppresses thermal damage to the target 4A. Therefore, by controlling the electron beam B to be incident on the thicker portion of the target 4 when the electron beam B1 penetrates to the deeper high-voltage portion, and to be incident on the thinner portion of the target 4 when the electron beam B2 only penetrates to the shallower low-voltage portion, the electron beam B can be incident on the appropriate position of the target 4 while suppressing thermal damage to the target 4.

[0062] Alternatively, the X-ray tube 1 can be configured as an open-transmission type X-ray tube or an open-reflection type X-ray tube. The open-transmission or open-reflection type X-ray tube 1 is configured such that the housing 2 can be opened, and it has replaceable components (e.g., window member 5, various parts of the electron gun 3). In the X-ray generating apparatus 10 equipped with the open-transmission or open-reflection type X-ray tube 1, the vacuum level inside the housing 2 is increased by a vacuum pump.

[0063] In either a sealed-through or open-through X-ray tube 1, the target 4 only needs to be formed in the area of ​​the second surface 52 of the window member 5 that is exposed at least in the opening 23. In either a sealed-through or open-through X-ray tube 1, the target 4 may also be formed on the second surface 52 of the window member 5 via other films.

[0064] Furthermore, in the example above, a permanent magnet 61 was shown as the magnetic field forming unit. However, any structure capable of forming a magnetic field between the cathode 32 and the target 4 (e.g., an electromagnet such as a coil) can be used as the magnetic field forming unit. Even if any structure is used, the formation (magnitude) of the magnetic field can be controlled without complex control, and electrons can be automatically incident to the appropriate position of the target 4 according to the tube voltage.

[0065] Furthermore, in the example above, one permanent magnet 61 was shown as the magnetic field forming unit. However, the number of permanent magnets 61 is not limited to this, and there may be multiple magnets, which can be arranged in a way that they are opposite to each other.

[0066] Furthermore, the distribution of the thickness T4 of the target 4 is arbitrary as described above, and is not limited to a distribution that thins from the central portion 4a toward the peripheral portion 4b as in the example above. For example, the distribution of the thickness T4 of the target 4 may also be a distribution that monotonically thins from one end to the other. In this case, if the target 4 is arranged such that electrons (electron beam B) are incident on the relatively thinner portion when the tube voltage is relatively high, the same effect is achieved.

[0067] Industrial availability

[0068] The present invention provides an X-ray generating apparatus that can avoid the complexity of control and direct the electron beam to the appropriate position of the target.

[0069] Explanation of symbols

[0070] 2…shell, 3…electron gun, 4…target, 5…window component, 10…X-ray generating device, 11…power supply unit (tube voltage application unit), 32…cathode (electron emission unit), 61…permanent magnet (magnetic field forming unit).

Claims

1. An X-ray generating device, wherein, have: case; An electron gun having an electron emission section that emits electrons from the housing; A target that generates X-rays within the housing through the incident electrons; A window component that seals the opening of the housing while allowing the X-rays to pass through; A tube voltage application section applies a tube voltage between the electron emission section and the target; and A magnetic field forming section is used to deflect the electrons by forming a magnetic field between the electron emission section and the target. The thickness of the target has a distribution. The target is configured such that, when the tube voltage is relatively high, electrons are incident on a relatively thin portion of the target's thickness when the tube voltage is relatively low. The thickness of the target decreases from the central portion, which intersects the axis of the electron gun, towards the periphery. The target is configured such that as the tube voltage relatively decreases, the electrons are incident on the peripheral side. The magnetic field forming section forms a fixed magnetic field containing a component perpendicular to the direction of electron travel.

2. The X-ray generating apparatus as claimed in claim 1, wherein, The magnetic field forming part contains a permanent magnet.

3. The X-ray generating apparatus as described in claim 1 or 2, wherein, The window member has a first surface opposite to the interior of the housing and a second surface on the interior side of the housing. The target is formed on the second surface.

4. The X-ray generating apparatus as described in claim 1 or 2, wherein, The target is supported in a tilted position relative to both the electron gun and the window member.

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