X-ray generator

Abstract

To provide an x-ray generator capable of causing an electron beam to enter an appropriate position on a target while avoiding complication of control.SOLUTION: An x-ray generator 10 includes an electron gun 3 having a cathode 32, a target 4 that generates X-rays upon incidence of electrons, a power supply unit 11 that applies a tube voltage between the cathode 32 and the target 4, and a permanent magnet 61 for deflecting the electrons (electron beam B) by creating a magnetic field between the cathode 32 and the target 4. The thickness T4 of the target 4 has distribution. The target 4 is arranged such that electrons are incident on a relatively thin portion of the target 4 with a thickness T4 when the tube voltage is relatively low than when the tube voltage is relatively high.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to x-ray generating devices. [Background technology]

[0002] Patent Document 1 describes a transmission type X-ray tube device. This device includes a vacuum envelope constituting an X-ray tube, an X-ray transmission window provided at one end of the vacuum envelope, a thin metal film forming an X-ray target provided 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-126650 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the device described in the above Patent Document 1, the metal thin film has a different thickness depending on the location, and a deflection electrode for deflecting the electron beam is provided. The deflection electrode is composed of a pair of electrode plates arranged to face each other between the target and the focusing electrode. As a result, in this device, the deflection voltage applied to the deflection electrode is changed according to the change in the acceleration voltage of the electron beam generated by the electron gun, so that the electron beam is incident on the target at a location with an appropriate thickness.

[0005] Thus, in the above technical field, there is a demand for the electron beam to be incident on a position of a target having an appropriate thickness according to its acceleration voltage. However, in the device described in Patent Document 1, in addition to controlling the acceleration voltage of the electron beam, it is necessary to adjust the deflection voltage to correspond to the acceleration voltage, which complicates the overall control.

[0006] Therefore, an object of the present disclosure is to provide an X-ray generating device that can cause an electron beam to be incident on an appropriate position on a target while avoiding complicated control. [Means for solving the problem]

[0007] The X-ray generating device according to the present disclosure comprises a housing, an electron gun having an electron emission unit that emits electrons within the housing, a target that generates X-rays within the housing by the incidence of electrons, a window member that seals an opening of the housing and allows X-rays to pass through, a tube voltage application unit that applies a tube voltage between the electron emission unit and the target, and a magnetic field forming unit that deflects electrons by forming a magnetic field between the electron emission unit and the target, wherein the target has a thickness distribution, and the target is positioned such that electrons are incident on a relatively thinner portion of the target when the tube voltage is relatively low compared to when the tube voltage is relatively high.

[0008] In this device, a tube voltage is applied between the electron emission part of the electron gun and the target by the tube voltage application part, and a magnetic field is formed between the electron emission part and the target by the magnetic field formation part. Therefore, even if the magnetic field formed by the magnetic field formation part is constant (for example, in time), if the electron acceleration changes by adjusting the tube voltage to a desired value and the electron speed changes, the radius of the circular motion of the electrons due to the Lorentz force changes. Therefore, the amount of electron deflection due to 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 circular motion of the electrons due to the Lorentz force becomes large, and as a result, the amount of electron deflection becomes small. On the other hand, when the tube voltage is relatively low and the electrons move at low speed, the radius of the circular motion of the electrons due to the Lorentz force becomes small, and as a result, the amount of electron deflection becomes large. In this way, in this device, the amount of electron deflection is automatically adjusted to correspond to the desired tube voltage without controlling the formation (magnitude) of the magnetic field by the magnetic field generation part. Therefore, by positioning a target having a thickness distribution so that electrons are incident on relatively thin parts of the target when the tube voltage is relatively low compared to when the tube voltage is relatively high, electrons can be incident on appropriate positions on the target (automatically) while avoiding complicated control.

[0009] In the X-ray generating device according to the present disclosure, the thickness of the target is made thinner from the center toward the periphery, and the target may be disposed so that electrons are incident on the periphery side as the tube voltage becomes relatively lower. In this case, it is easy to form the target so that the thickness of the target has the above-mentioned distribution.

[0010] In the X-ray generating device according to the present disclosure, the magnetic field forming unit may include a permanent magnet. In this manner, in this device, it is sufficient that a constant magnetic field is formed by the permanent magnet, and it is possible to reliably avoid complicating the control.

[0011] In the X-ray generating device according to the present disclosure, the window member may have a first surface on the opposite side to the inside of the housing and a second surface on the inside of the housing, and the target may be formed on the second surface, forming a so-called transmission type X-ray generating device.

[0012] In the X-ray generator according to the present disclosure, the target may be supported in an inclined state so as to face both the electron gun and the window member, forming a so-called reflection type X-ray generator. Effect of the Invention

[0013] According to the present disclosure, it is possible to provide an X-ray generating device that can cause an electron beam to be incident on an appropriate position on a target while avoiding complicated control. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a block diagram of an X-ray generating device according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of the X-ray tube shown in FIG. [Diagram 3] FIG. 2 is a schematic diagram for explaining the relationship between an electron beam and a target. [Figure 4] FIG. 3 is a schematic side view showing an enlarged view of a part of FIG. 2. [Diagram 5] FIG. 11 is a cross-sectional view of a modified X-ray tube. [Figure 6] FIG. 6 is a schematic side view showing an enlarged view of a part of FIG. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and duplicated explanations will be omitted. [X-ray generator configuration]

[0016] 1, the X-ray generating device 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 in a case (not shown) made of metal. As an example, the X-ray tube 1 is a small focus X-ray source, and the X-ray generating device 10 is a device used in X-ray nondestructive inspection for magnifying and observing the internal structure of an inspection target.

[0017] 2, the X-ray tube 1 includes a housing 2, an electron gun 3, a target 4, and a window member 5. As described below, the X-ray tube 1 is configured as a sealed transmission type X-ray tube that does not require replacement of parts.

[0018] The housing 2 has a head 21 and a bulb 22. The head 21 is formed of metal in a cylindrical shape with a bottom. The bulb 22 is formed of an insulating material such as glass in a cylindrical shape with a bottom. An opening 22a of the bulb 22 is airtightly joined to an opening 21a of the head 21. In the X-ray tube 1, the center line of the housing 2 is the tube axis A. An opening 23 is formed in the bottom wall portion 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 has, for example, a circular shape with the tube axis A as its center line.

[0019] The electron gun 3 emits an electron beam B in the housing 2. The electron gun 3 has a heater 31, a cathode 32, a first grid electrode 33, and a second grid electrode 34. The heater 31, the cathode 32, the first grid electrode 33, and the second grid electrode 34 are arranged on the tube axis A in this order from the bottom wall portion 22b side of the bulb 22. As an example, the axis A3 of the electron gun 3 (see FIG. 4) coincides with the tube axis A. The axis A3 of the electron gun 3 may be defined as, for example, the central axis of the electron gun 3 (for example, the central axis of the cathode 32, the first grid electrode 33, and the second grid electrode 34), or may be defined as the trajectory of the electron beam B when the electron beam B is not deflected as described later. The heater 31 is formed of a filament, and generates heat when electricity is applied. The cathode 32 is heated by the heater 31 and emits electrons. In other words, the cathode 32 is an electron emitting part that emits electrons within the housing 2.

[0020] The first grid electrode 33 is formed in a cylindrical shape and adjusts the amount of electrons emitted from the cathode 32. The first grid electrode 33 also serves as an extraction electrode for extracting electrons emitted from the cathode 32. The initial velocity of the electrons is determined according to a voltage (extraction voltage) applied to the first grid electrode 33. The second grid electrode 34 is formed in a cylindrical shape and focuses the electrons that have passed through the first grid electrode 33 onto the target 4. The heater 31, the cathode 32, the first grid electrode 33, and the second grid electrode 34 are each electrically and physically connected to a plurality of lead pins 35 penetrating the bottom wall portion 22b of the bulb 22. Each of the lead pins 35 is electrically connected to the power supply unit 11 of the X-ray generating device 10.

[0021] The window member 5 seals the opening 23 of the housing 2. The window member 5 is formed in a plate shape from a material with high X-ray transparency, such as diamond or beryllium. The window member 5 is, for example, in a disk shape with the tube axis A as the center line. The window member 5 has a first surface 51 and a second surface 52. The first surface 51 is a surface on the opposite side to the inside of the housing 2, and the second surface 52 is a surface on the inside side of the housing 2. Each of the first surface 51 and the second surface 52 is, for example, a flat surface perpendicular to the tube axis A. The target 4 is formed on the second surface 52 of the window member 5. The target 4 is, for example, formed in a film shape from tungsten. The target 4 generates X-rays R by the incidence of the electron beam B in the housing 2. In this embodiment, the X-rays R generated in the target 4 are transmitted through the target 4 and the window member 5 and emitted to the outside.

[0022] The window member 5 is attached to a mounting surface 24 around the opening 23 in the housing 2. The mounting surface 24 is, for example, a flat surface perpendicular to the tube axis A, and is formed on the head 21. The window member 5 can be hermetically joined to the mounting surface 24 via a joining member (not shown) such as a 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 set to a ground potential via the head 21. As a result, a tube voltage is applied between the cathode 32 of the electron gun 3 and the target 4.

[0023] The tube voltage defines the acceleration of electrons emitted from the cathode 32 toward the target 4. In the X-ray generating device 10, the power supply unit 11 supplies a negative voltage to the cathode 32 via the lead pin 35, and the target 4 (anode) is set to a ground potential, so that the tube voltage is applied between the cathode 32 and the target 4. In this manner, the power supply unit 11 constitutes a tube voltage application unit that applies the tube voltage in cooperation with the cathode 32 and the target 4. On the other hand, the power supply unit 11 is also connected to the first grid electrode 33 as an extraction electrode, and applies an extraction voltage to the first grid electrode 33. Therefore, the power supply unit 11 constitutes an extraction voltage application unit. Note that, as an example, heat generated in the target 4 by the incidence of the electron beam B is transferred to the head 21 directly or via the window member 5, and is further released from the head 21 to a heat dissipation unit (not shown). In this embodiment, the space inside the housing 2 is maintained at a high vacuum by the housing 2, the target 4, and the window member 5.

[0024] In the X-ray generator 10 configured as above, a negative voltage is applied to the electron gun 3 by the power supply unit 11 with the potential of the target 4 as a reference. As an example, the power supply unit 11 applies a negative high voltage (e.g., −10 kV to −500 kV) to each part of the electron gun 3 via each lead pin 35 while the target 4 is at ground potential. The electron beam B emitted from the electron gun 3 is focused on the target 4 along the tube axis A. The X-rays R generated in the area of ​​the target 4 irradiated with the electron beam B are focused at the irradiated area and transmitted through the target 4 and the window member 5 to be emitted to the outside.

[0025] Here, the X-ray tube 1 includes a deflection unit 6. The deflection unit 6 has a permanent magnet 61. The permanent magnet 61 is made of, for example, a ferrite magnet, a neodymium magnet, a samarium-cobalt magnet, an alnico magnet, or the like.

[0026] The permanent magnet 61 is disposed outside the housing 2, and is fixed to a flange portion of the head 21, for example, via a fixing portion not shown. This allows the permanent magnet 61 to be attached to the outside of the housing 2. In particular, 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 including at least a component perpendicular to the traveling direction of the electrons is formed between the cathode 32 and the target 4. In this way, the permanent magnet 61 functions as a magnetic field forming portion for deflecting the electrons by forming a magnetic field between the cathode 32 and the target 4.

[0027] The deflection unit 6 deflects the electron beam B by the magnetic field formed by the permanent magnet 61, and changes the position of incidence of the electron beam B on the target 4. When viewed from a direction perpendicular to the path of the electron beam B emitted from the cathode 32 and traveling to the target 4 (radial direction), the deflection unit 6 preferably includes a portion overlapping the path. This allows the magnetic field formed by the permanent magnet 61 to suitably apply a force to the electron beam B. In this example, the deflection unit 6 is arranged so that the entire deflection unit 6 is included in the path of the electron beam B when viewed from the radial direction. Note that the deflection unit 6 is not limited to being arranged so as to include a portion overlapping the path of the electron beam B when viewed from the radial direction, as long as it can form a magnetic field that deflects the electron beam B. For example, in FIG. 2, when the emission direction of the X-ray R is the upper side and the opposite side is the lower side in the direction along the tube axis A, the deflection unit 6 may be arranged below the bottom wall portion 22b of the bulb 22. The deflection unit 6 may be rotatable around the tube axis A. In this case, by rotating the deflection unit 6, it is possible to adjust the incident position of the electron beam B on the target 4. [Target configuration]

[0028] Next, the relationship between the electron beam and the target will be described in conjunction with the configuration of the target. In an X-ray generator, the energy of the generated X-ray varies depending on the tube voltage, so the tube voltage may be changed within a range of, for example, 40 kV to 130 kV. As shown in FIG. 3, the penetration depth of the electron beam B1 into the target 4A when accelerated at a relatively high tube voltage is deeper than that of the electron beam B2 when accelerated at a relatively low tube voltage.

[0029] Therefore, as shown in FIG. 3(a), when the target 4A is relatively thick, the electron beam B1 at the time of high tube voltage penetrates into the target 4A so as to reach the vicinity of the boundary between the target 4A and the support 5A (corresponding to the window member 5 here) (the deepest part of the target 4A). That is, the penetration depth is appropriate for the thickness of the target 4A. That is, since the thickness of the target 4A through which the X-rays generated in the target 4A must pass before reaching the support 5A is small, the decrease in the X-ray output due to self-absorption by the target 4A is suppressed. On the other hand, the penetration depth of the electron beam B2 at the time of low tube voltage remains near the surface of the target 4A, and since the thickness of the target 4A through which the X-rays generated in the target 4A must pass before reaching the support 5A is large, there is a risk of the X-ray output decreasing due to self-absorption by the target 4A.

[0030] Furthermore, since most of the energy of the electron beam B is converted into heat, if the heat is stored in the target 4A, the target 4A may be thermally damaged. Therefore, by penetrating the target 4A to reach the vicinity of the boundary between the target 4A and the support 5A, as in the case of the electron beam B1, the generated heat is easily transferred to the support 5A, and the target 4A can be prevented from being thermally damaged. On the other hand, the penetration depth of the electron beam B2 at low tube voltage remains near the surface of the target 4A, so that the generated heat is not easily transferred to the support 5A, and the target 4A may be thermally damaged. Thus, when the target 4A is relatively thick, it is preferable for the electron beam B1 at high tube voltage, but not preferable for the electron beam B2 at low tube voltage. In order to efficiently release the heat generated inside the target 4A, it is preferable that the support 5A is made of a material with good thermal conductivity, such as diamond.

[0031] Also, as shown in (b) of Fig. 3, when the target 4B is relatively thin, even the electron beam B2 at a low tube voltage penetrates into the target 4B so as to reach the vicinity of the boundary between the target 4B and the support 5A (the deepest part of the target 4A). In other words, the penetration depth is appropriate for the thickness of the target 4B. On the other hand, the electron beam B1 at a high tube voltage penetrates the target 4B, resulting in a decrease in X-ray output compared to the case of (a) of Fig. 3.

[0032] In response to this, it is possible to configure the thickness of the target 4C to be non-uniform, as shown in FIG. 3(c). In other words, it is possible to generate a distribution in the thickness of the target 4C. In this way, if the electron beam B1 at the time of high tube voltage is incident on a relatively thick position of the target 4C and the electron beam B2 at the time of low tube voltage is incident on a relatively thin position of the target 4C, both electron beams can penetrate into the target 4C to reach the vicinity of the boundary between the target 4C and the support 5A. Therefore, it is possible to suppress a decrease in X-ray output over a wide range of tube voltages, and to suppress thermal damage to the target 4C.

[0033] 4, the X-ray generator 10 is configured so that the thickness T4 of the target 4 has a predetermined distribution. That is, the thickness T4 of the target 4 has a distribution so that it changes depending on the position in a plane intersecting with the axis A3 (tube axis A) which is the center line of the electron gun 3. The distribution may be in any manner, but in the illustrated example, the thickness T4 of the target 4 becomes thinner from the central portion 4a to the peripheral portion 4b when viewed from the direction intersecting with the axis A3.

[0034] In the X-ray generator 10, the target 4 is disposed so that the relationship between the incidence positions of the electron beams B1 and B2 on the target 4 is appropriate. That is, the target 4 is disposed so that the electron beam B1 at a high tube voltage is incident on a relatively thick portion of the target 4, and the 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 generator 10, the target 4 is disposed so that the electrons (electron beam B) are incident on a relatively thinner portion of the thickness of the target 4 when the tube voltage is relatively low than when the tube voltage is relatively high. Note that in FIG. 4, various parts are omitted, including the first grid electrode 33 and the second grid electrode 34 of the electron gun 3.

[0035] The target 4 having the thickness distribution as described above can be manufactured, for example, as follows. That is, when forming the target 4 by depositing a film on a support (here, the window member 5), a mask corresponding to the peripheral portion of the target 4 is used. The portion of the support overlapping with the mask has poor visibility when viewed from the deposition source, preventing film deposition, and the film is deposited thinner than in the central portion not overlapping with the mask. In this way, the target 4 can be manufactured so that it is thicker in the center and thinner in the peripheral portion. The difference in thickness (aspect ratio) between the central portion and the peripheral portion can be controlled by the position where the mask is placed, the thickness of the mask, etc. [Action and Effects]

[0036] In the X-ray generator 10, a tube voltage is applied between the cathode 32 of the electron gun 3 and the target 4 by the tube voltage application unit (power supply unit 11), and a magnetic field is formed between the cathode 32 and the target 4 by the permanent magnet 61 of the deflection unit 6. Therefore, if the acceleration of the electrons is changed by adjusting the tube voltage to a desired value, and the electron speed is changed, the radius of the circular motion of the electrons due to the Lorentz force is changed, and the amount of electron deflection due to the magnetic field is automatically changed as well.

[0037] For example, when the tube voltage is relatively high and the electrons move at high speed, the radius of the circular motion of the electrons due to the Lorentz force becomes large, and as a result, the amount of deflection of the electrons becomes small. On the other hand, when the tube voltage is relatively low and the electrons move at low speed, the radius of the circular motion of the electrons due to the Lorentz force becomes small, and as a result, the amount of deflection of the electrons becomes large. In this way, the amount of deflection of the electrons is automatically adjusted to correspond to the desired tube voltage without controlling the formation (magnitude) of the magnetic field by the X-ray generator 10 and the permanent magnet 61. Therefore, the target 4 having a thickness distribution is arranged so that the electrons are incident on the part of the target where the thickness is relatively thin when the tube voltage is relatively low compared to when the tube voltage is relatively high, and thus the electrons can be incident on the appropriate position of the target 4 (automatically) while avoiding complicated control.

[0038] An example of the optimal value of the thickness T4 of the target 4 at the electron incidence position is about 2 μm when the tube voltage is about 40 kV, and about 10 μm when the tube voltage is about 130 kV. Therefore, the target 4 can be formed so that the thickness T4 is distributed in the range from 2 μm to 10 μm.

[0039] In the X-ray generating device 10, the thickness T4 of the target 4 is made thinner from the central portion 4a toward the peripheral portion 4b, and the target 4 is disposed so that electrons are incident on the peripheral portion 4b as the tube voltage becomes relatively lower. This makes it easy to form the target 4 so that the thickness T4 of the target 4 has the above-mentioned distribution.

[0040] Furthermore, the X-ray generating device 10 includes, as a magnetic field forming unit, a permanent magnet 61 attached to the housing 2 between the cathode 32 and the target 4. Therefore, in the X-ray generating device 10, it is sufficient that a constant magnetic field is formed by the permanent magnet 61, and complicating control can be reliably avoided.

[0041] In the X-ray generating device 10, the window member 5 has a first surface 51 on the side opposite to the inside of the housing 2 and a second surface 52 on the inside side of the housing 2, and the target 4 is formed on the second surface 52. In this way, a so-called transmission type X-ray generating device 10 is configured. [Variations]

[0042] The present disclosure is not limited to the above embodiment. The X-ray tube 1 and the X-ray generator 10 may be configured as a sealed reflection type. As shown in FIG. 5, the sealed reflection type X-ray tube 1 is mainly different from the sealed transmission type X-ray tube 1 in that the electron gun 3 is disposed in a housing section 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 section 7 has a side tube 71 and a stem 72. The side tube 71 is joined to the side wall of the head 21 so that one opening 71a of the side tube 71 faces the inside of the head 21. The stem 72 seals the other opening 71b of the side tube 71.

[0043] The heater 31, cathode 32, first grid electrode 33, and second grid electrode 34 are arranged in this order from the stem 72 side inside the side tube 71. A plurality of lead pins 35 penetrate the stem 72. The support member 8 penetrates the bottom wall 22b of the bulb 22. The target 4 is fixed to the tip 81 of the support member 8 in a state inclined so as to face both the electron gun 3 and the window member 5 on the tube axis A.

[0044] In this example, the deflection unit 6 is provided with respect to the side tube 71 of the accommodation unit 7. As a result, the permanent magnet 61 is disposed between the cathode 32 and the target 4 by the holding member 62. As a result, a magnetic field including at least a component perpendicular to the traveling direction of the electrons is formed between the cathode 32 and the target 4. In this way, the permanent magnet 61 also functions here as a magnetic field forming unit for deflecting the electrons by forming a magnetic field between the cathode 32 and the target 4.

[0045] More specifically, as shown in Fig. 6, the permanent magnet 61 is disposed outside the side tube 71 of the housing unit 7. Therefore, the electrons emitted from the cathode 32 are deflected by a force from the magnetic field formed by the permanent magnet 61, at least within the side tube 71. Note that Fig. 6 omits various components, including the first grid electrode 33 and the second grid electrode 34 of the electron gun 3.

[0046] Furthermore, similar to the above embodiment, the target 4 has a distribution in thickness T4, and is arranged so that electrons (electron beam B) are incident on a relatively thinner portion when the tube voltage is relatively low compared to when the tube voltage is relatively high.

[0047] In the X-ray generator 10 equipped with the sealed reflection type X-ray tube 1 configured as described above, as an example, with the head 21 and the side tube 71 at ground potential, a positive voltage is applied to the target 4 by the power supply unit 11 via the support member 8, and a negative voltage is applied to each part of the electron gun 3 by the power supply unit 11 via a plurality of lead pins 35. The electron beam B emitted from the electron gun 3 is focused on the target 4 along a direction perpendicular to the tube axis A. The X-ray R generated in the irradiation area of ​​the electron beam B on the target 4 is emitted to the outside through the window member 5 with the irradiation area as the focus. When X-rays are generated by electrons incident on the target 4, most of the incident energy is converted into heat, so that if heat is stored in the target 4, the target 4 may be thermally damaged. As a measure against heat dissipation, 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 used for the support 5A. 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 so as to reach the vicinity of the boundary between the target 4A and the support 5A, which makes it easier to transfer the generated heat to the support 5A and suppresses thermal damage to the target 4A. Therefore, by controlling the electron beam B to be incident on a thick portion of the target 4 at high tube voltage when the electron beam B1 penetrates deeply, and on a thin portion of the target 4 at low tube voltage when the electron beam B2 penetrates only to a shallow position, the electron beam B can be incident on an appropriate position of the target 4 and thermal damage to the target 4 can be suppressed.

[0048] The X-ray tube 1 may be configured as an open transmission type X-ray tube or an open reflection type X-ray tube. The open transmission type or open reflection type X-ray tube 1 is an X-ray tube in which the housing 2 is configured to be openable and parts (for example, the window member 5 and each part of the electron gun 3) can be replaced. In an X-ray generating device 10 including an open transmission type or open reflection type X-ray tube 1, the degree of vacuum in the space inside the housing 2 is increased by a vacuum pump.

[0049] In a sealed transmission type or open transmission type X-ray tube 1, the target 4 may be formed on at least a region of the second surface 52 of the window member 5 that is exposed to the opening 23. In a sealed transmission type or open transmission type X-ray tube 1, the target 4 may be formed on the second surface 52 of the window member 5 via another film.

[0050] In the above example, the permanent magnet 61 is exemplified as the magnetic field forming unit. However, any configuration (for example, an electromagnet such as a coil) capable of forming a magnetic field between the cathode 32 and the target 4 may be adopted as the magnetic field forming unit. Regardless of the configuration of the magnetic field forming unit adopted, electrons can be automatically injected into an appropriate position of the target 4 according to the tube voltage without controlling the formation (magnitude) of the magnetic field, that is, while avoiding complicated control.

[0051] In the above example, one permanent magnet 61 is illustrated as the magnetic field generating unit. However, the number of permanent magnets 61 is not limited to this, and there may be a plurality of permanent magnets 61. In this case, the permanent magnets 61 may be arranged to face each other.

[0052] Furthermore, the distribution of the thickness T4 of the target 4 may be any as described above, and is not limited to the distribution that becomes thinner from the central portion 4a toward the peripheral portion 4b as in the above example. For example, the distribution of the thickness T4 of the target 4 may be a distribution that becomes monotonically thinner from one end to the other end. Even in this case, the same effect can be achieved by arranging the target 4 so that the electrons (electron beam B) are incident on the relatively thinner portion when the tube voltage is relatively low rather than when the tube voltage is relatively high. [Explanation of symbols]

[0053] 2...housing, 3...electron gun, 4...target, 5...window member, 10...X-ray generator, 11...power supply unit (tube voltage application unit), 32...cathode (electron emission unit), 61...permanent magnet (magnetic field formation unit).

Claims

1. A housing and an electron gun having an electron emission unit that emits electrons within the housing; a target that generates X-rays in response to the electrons being incident on the target within the housing; a window member that seals an opening of the housing and allows the X-rays to pass through; a tube voltage application unit that applies a tube voltage between the electron emission unit and the target; a magnetic field forming unit for forming a magnetic field between the electron emission unit and the target to deflect the electrons; Equipped with The target has a thickness distribution, the target is disposed such that the electrons are incident on a relatively thinner portion of the target when the tube voltage is relatively low than when the tube voltage is relatively high; The thickness of the target is made thinner from a central portion intersecting an axis of the electron gun toward a peripheral portion, the target is disposed such that the electrons are incident on the peripheral portion side as the tube voltage becomes relatively lower, The magnetic field forming unit forms a constant magnetic field including a component perpendicular to the direction of travel of the electrons. X-ray generator.

2. The magnetic field forming unit includes a permanent magnet.

2. The X-ray generating device according to claim 1.

3. the window member has a first surface opposite to an interior of the housing and a second surface on an interior side of the housing; The target is formed on the second surface.

3. The X-ray generating device according to claim 1 or 2.

4. the target is supported in an inclined state so as to face both the electron gun and the window member; 3. The X-ray generating device according to claim 1 or 2.

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