X-ray generating device

Abstract

The X-ray generating device of the present invention comprises: an electron gun having a cathode for emitting an electron beam; a first housing that houses the electron gun; a target onto which the electron beam emitted from the electron gun is incident; a second housing that houses the target; and an electron passageway provided across the first and second housings for passing the electron beam from a first internal space of the first housing toward a second internal space of the second housing. The electron passageway has a diameter-reducing portion that reduces the diameter toward the target. The first housing is provided with a first exhaust flow path for vacuum-exhausting the first internal space within the first housing. The second housing is provided with a second exhaust flow path for vacuum-exhausting the second internal space within the second housing.

Description

Technical Field

[0001] One aspect of the present disclosure relates to an X-ray generating device. Background Art

[0002] An X-ray generator that generates X-rays by causing an electron beam emitted from a cathode to enter a target is known. For example, Patent Document 1 describes that a portion of the electron beam entering a target is emitted from the target as reflected electrons.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 11-144653 Summary of the Invention

[0006] Problems that the invention aims to solve

[0007] If reflected electrons emitted from the target reach the cathode, there's a concern that these reflected electrons could degrade the cathode. Therefore, some X-ray generators use magnetic field generators, which use the Lorentz force to deflect the reflected electrons and redirect them to the target. However, sufficient deflection of the reflected electrons requires a relatively large space to accommodate the magnetic field generator, leading to concerns about increased manufacturing costs.

[0008] This specification discloses an example of an X-ray generating apparatus that can suppress degradation of a cathode caused by reflected electrons emitted from a target.

[0009] Technical means to solve problems

[0010] An exemplary X-ray generating device may include: an electron gun having a cathode that emits an electron beam; a first housing that houses the electron gun; a target onto which the electron beam emitted from the electron gun is incident; and a second housing that houses the target. For example, the electron gun may be mounted on the first housing, or at least partially disposed within the first housing, and the target may be mounted on the second housing, or at least partially disposed within the second housing. Furthermore, the X-ray generating device may include an electron passage extending across the first and second housings, allowing the electron beam to pass from the first internal space of the first housing to the second internal space of the second housing. The electron passage includes a diameter-reducing portion that decreases in diameter toward the target. A first exhaust flow path is provided in the first housing for evacuating the first internal space within the first housing. A second exhaust flow path is provided in the second housing for evacuating the second internal space within the second housing.

[0011] In order to suppress or prevent the degradation of the cathode, the number of reflected electrons can be reduced. The reflected electrons are generated in the second frame due to the electron beam incident on the target and reach the first frame via the electron passage path. In addition, gas is generated in the second frame due to the collision of electrons toward the target. However, since the entrance on the target side of the electron passage path is narrowed, it is difficult to attract the above-mentioned gas toward the first frame side via the electron passage path and discharge the above-mentioned gas from the first exhaust flow path provided in the first frame. Therefore, the exhaust path (second exhaust flow path) for the above-mentioned gas is provided in the second frame itself. Thus, vacuum exhaust can be performed in each frame, and the degradation of the cathode caused by the reflected electrons can be suppressed or prevented.

[0012] An exemplary X-ray generator may further include a magnetic focusing lens that surrounds the electron path after the electron gun and focuses the electron beam. A portion of the electron path has an expanded diameter portion located between the electron gun and the pole piece of the magnetic focusing lens, which expands toward the target. Thus, even if reflected electrons enter the path from the target-side end of the path, the expanded diameter portion, which expands toward the target (i.e., the portion that contracts toward the cathode), suppresses or prevents the reflected electrons from traveling toward the cathode through the path.

[0013] The expanded diameter portion can discontinuously change from a first diameter to a second diameter that is larger than the first diameter. This allows even if reflected electrons traveling from the target toward the electron gun exist within the electron path, these reflected electrons can collide with the portion that discontinuously changes from the first diameter to the second diameter. In some examples, the expanded diameter portion that changes from the first diameter to the second diameter includes an annular wall having the first diameter as its inner diameter and the second diameter as its outer diameter. This can more effectively suppress or prevent these reflected electrons from moving toward the cathode.

[0014] An exemplary X-ray generating device may further include a magnetic focusing lens that surrounds the electron path after the electron gun to focus the electron beam. The diameter of the region of the electron path enclosed by the pole piece of the magnetic focusing lens may be equal to the maximum diameter of the electron path. In some examples, by making the diameter of the region of the electron path enclosed by the pole piece equal to the maximum diameter of the electron path, the electron beam bounding the target can be effectively suppressed or prevented from impacting the inner wall of the electron path. The region of the electron path enclosed by the pole piece may include a region where the divergence of the electron beam emitted from the electron gun is increased.

[0015] An exemplary X-ray generating device may further include an exhaust unit that vacuum-exhausts the first internal space of the first housing via a first exhaust flow path and vacuum-exhausts the second internal space of the second housing via a second exhaust flow path. The first exhaust flow path and the second exhaust flow path may be interconnected. In some examples, both the first internal space within the first housing and the second internal space within the second housing can be vacuum-exhausted via a common exhaust unit, thereby miniaturizing the device.

[0016] Effects of the Invention

[0017] This can suppress or prevent degradation of the cathode due to reflected electrons emitted from the target. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic structural diagram of an exemplary X-ray generating device.

[0019] Figure 2 This is a schematic cross-sectional view showing a configuration example of a magnetic lens of an X-ray generator.

[0020] Figure 3 is a front view of an exemplary magnetic quadrupole lens.

[0021] Figure 4 Schematic diagram of the structure (doublet lens) of the embodiment and the comparative example including the magnetic focusing lens and the magnetic quadrupole lens.

[0022] Figure 5 This is a diagram showing an example of the relationship between the cross-sectional shape of an electron beam and the shape of an effective focal point of X-rays.

[0023] Figure 6 It is a diagram showing a first variation of the cylindrical tube.

[0024] Figure 7 It is a diagram showing a second variation of the cylindrical tube.

[0025] Figure 8 This is a schematic structural diagram of an X-ray generating device according to a modified example. DETAILED DESCRIPTION

[0026] In the following description, the same or corresponding elements are denoted by the same reference numerals with reference to the drawings, and redundant description is omitted.

[0027] like Figure 1As shown, the exemplary X-ray generator 1 includes an electron gun 2, a rotating anode unit 3, a magnetic lens 4, an exhaust section 5, a housing 6 (first housing) defining an interior space S1 for accommodating the electron gun 2, and a housing 7 (second housing) defining an interior space S2 for accommodating the rotating anode unit 3. The housings 6 and 7 may be detachable from each other, integrally coupled to each other in a non-detachable manner, or integrally formed from the outset.

[0028] The electron gun 2 emits an electron beam EB. The electron gun 2 has a cathode C that emits the electron beam EB. The cathode C is a circular planar cathode that emits an electron beam EB having a circular cross-sectional shape. The so-called cross-sectional shape of the electron beam EB refers to the cross-sectional shape in the direction perpendicular to the X-axis direction (first direction) which is parallel to the direction of travel of the electron beam EB described later. That is, the cross-sectional shape of the electron beam EB is the shape within the YZ plane. In order to form an electron beam EB having a circular cross-sectional shape, for example, the electron emission surface of the cathode C itself may have a circular shape when observed from a position opposite to the electron emission surface of the cathode C (the electron emission surface of the cathode C is observed from the X-axis direction).

[0029] The rotating anode unit 3 includes a target 31, a rotating support 32, and a drive unit 33 that rotates the rotating support 32 about a rotation axis A. The target 31 is disposed along the periphery of the rotating support 32, which is formed in a flat truncated cone shape with the rotation axis A as its center axis. The rotation axis A is the central axis of the rotating support 32, and the side surfaces of the truncated cone-shaped rotating support 32 have surfaces inclined relative to the rotation axis A. Alternatively, the rotating support 32 may be formed in a ring shape with the rotation axis A as its center axis. The target 31 is made of, for example, heavy metals such as tungsten, silver, rhodium, molybdenum, and alloys thereof. The rotating support 32 is rotatable about the rotation axis A. The rotating support 32 is made of, for example, a metal such as copper or a copper alloy. The drive unit 33 includes a drive source such as a motor and rotates the rotating support 32 about the rotation axis A. As the rotating support 32 rotates, the target 31 receives the electron beam EB and generates X-rays XR. X-rays XR are emitted from the X-ray passage hole 7a formed in the frame 7 toward the outside of the frame 7. The X-ray passage hole 7a is sealed airtightly by a window member 8. The axial direction of the rotation axis A is parallel to the incident direction of the electron beam EB toward the target 31. However, the rotation axis A may be tilted so as to extend in a direction intersecting the incident direction relative to the incident direction of the electron beam EB toward the target 31. The target 31 may be a so-called reflective type that emits X-rays XR in a direction intersecting the direction of travel of the electron beam EB (the direction of incidence toward the target 31). In some embodiments, the emission direction of the X-rays XR is a direction orthogonal to the direction of travel of the electron beam EB. Therefore, the direction parallel to the direction of travel of the electron beam EB is set as the X-axis direction (first direction), the direction parallel to the emission direction of the X-rays XR from the target 31 is set as the Z-axis direction (second direction), and the direction orthogonal to the X-axis direction and the Z-axis direction is set as the Y-axis direction (third direction).

[0030] The magnetic lens 4 controls the electron beam EB. The magnetic lens 4 includes a deflection coil 41, a magnetic focusing lens 42, a magnetic quadrupole lens 43, and a frame 44. The frame 44 houses the deflection coil 41, the magnetic focusing lens 42, and the magnetic quadrupole lens 43. The deflection coil 41, the magnetic focusing lens 42, and the magnetic quadrupole lens 43 are arranged in sequence along the X-axis direction, from the electron gun 2 side to the target 31 side. An electron passage P is formed between the electron gun 2 and the target 31, through which the electron beam EB passes. Figure 2 As shown, the electron passage P can be formed by a cylindrical tube 9 (cylindrical portion). The cylindrical tube 9 is a non-magnetic metal member extending along the X-axis between the electron gun 2 and the target 31. The details of the additional exemplary structure of the cylindrical tube 9 will be described later.

[0031] The deflection coil 41, magnetic focusing lens 42, and magnetic quadrupole lens 43 are directly or indirectly connected to the cylindrical tube 9. For example, by assembling the deflection coil 41, magnetic focusing lens 42, and magnetic quadrupole lens 43 with reference to the cylindrical tube 9, their respective central axes are precisely aligned coaxially. Consequently, the central axes of the deflection coil 41, magnetic focusing lens 42, and magnetic quadrupole lens 43 coincide with the central axis of the cylindrical tube 9 (an axis parallel to the X-axis).

[0032] The deflection coil 41 is arranged between the electron gun 2 and the magnetic focusing lens 42. The deflection coil 41 is arranged so as to surround the electron passage path P. For example, the deflection coil 41 is indirectly connected to the cylindrical tube 9 via the cylindrical member 10. The cylindrical member 10 is a non-magnetic metal member extending coaxially with the cylindrical tube 9. The cylindrical member 10 is provided to cover the outer circumference of the cylindrical tube 9. The deflection coil 41 is positioned by the surface of the wall portion 44a on the target 31 side and the outer circumferential surface of the cylindrical member 10. The wall portion 44a is a part of the frame 44 arranged at a position opposite to the internal space S1 and is composed of a non-magnetic material. The deflection coil 41 adjusts the direction of travel of the electron beam EB emitted from the electron gun 2. The deflection coil 41 may include one (one group) of deflection coils or two (two groups) of deflection coils. In the former case, where the deflection coil 41 comprises a single deflection coil, the deflection coil 41 can be configured to correct for angular misalignment between the exit axis of the electron beam EB emitted from the electron gun 2 and the central axis (axis parallel to the X-axis) of the magnetic focusing lens 42 and the magnetic quadrupole lens 43. For example, angular misalignment can occur when the exit axis and the central axis intersect at a specific angle. Therefore, the angular misalignment can be eliminated by using the deflection coil 41 to change the direction of travel of the electron beam EB to a direction along the central axis. In the latter case, where the deflection coil 41 comprises two deflection coils, the deflection coil 41 can perform two-dimensional deflection. Therefore, not only can the angular misalignment be corrected, but also lateral misalignment between the exit axis and the central axis (for example, when the exit axis and the central axis are parallel in the X-axis direction and spaced apart in one or both of the Y-axis and Z-axis directions) can be appropriately corrected.

[0033] The magnetic focusing lens 42 is arranged at a rearward position relative to the electron gun 2 and the deflection coil 41. The magnetic focusing lens 42 focuses the electron beam EB while rotating it around an axis along the X-axis. For example, the electron beam EB passing through the magnetic focusing lens 42 is focused while rotating in a spiral pattern. The magnetic focusing lens 42 includes a coil 42a, a pole piece 42b, a yoke 42c, and a yoke 42d, arranged to surround the electron path P. The yoke 42c also functions as a wall 44b of the frame 44, which is provided to connect a portion of the outer side of the coil 42a to the cylindrical member 10. The yoke 42d is a cylindrical member provided to cover the outer circumference of the cylindrical member 10. For example, the coil 42a is indirectly connected to the cylindrical tube 9 via the cylindrical member 10 and the yoke 42d. The pole piece 42b includes the yoke 42c and the yoke 42d. The yoke 42c and the yoke 42d are ferromagnetic materials such as iron. Alternatively, pole piece 42b may include a notch (gap) between yoke 42c and yoke 42d, and portions of yoke 42c and yoke 42d located near the notch. The inner diameter D of pole piece 42b is equal to the inner diameter of the region adjacent to the gap between yoke 42c or yoke 42d. Therefore, magnetic focusing lens 42 may be configured so that the magnetic field of coil 42a leaks from pole piece 42b toward cylindrical tube 9.

[0034] The magnetic quadrupole lens 43 is arranged at a rear section relative to the magnetic focusing lens 42. The magnetic quadrupole lens 43 deforms the cross-sectional shape of the electron beam EB into an elliptical shape having a major diameter along the Z-axis direction and a minor diameter along the Y-axis direction. The magnetic quadrupole lens 43 is arranged so as to surround the electron passage path P. For example, the magnetic quadrupole lens 43 is indirectly connected to the cylindrical tube 9 via the wall portion 44c of the frame 44. The wall portion 44c is arranged to be connected to the wall portion 44b and to cover the outer circumference of the cylindrical tube 9. The wall portion 44c comprises a non-magnetic metal material.

[0035] like Figure 3As shown, the exemplary magnetic quadrupole lens 43 comprises an annular yoke 43a, four cylindrical yokes 43b disposed on the inner circumference of yoke 43a, and a yoke 43c disposed at the tip of each yoke 43b. A coil 43d is wound around the yoke 43b. Each yoke 43c has a roughly semicircular cross-section in the YZ plane. The inner diameter d of the magnetic quadrupole lens 43 is the diameter of the inscribed circle passing through the innermost end of each yoke 43c. The magnetic quadrupole lens 43 functions as a concave lens in the XZ plane (a plane perpendicular to the Y-axis direction) and as a convex lens in the XY plane (a plane perpendicular to the Z-axis direction). This function of the magnetic quadrupole lens 43 adjusts the aspect ratio between the diameter of the electron beam EB in the Z-axis direction (the major diameter X1) and the diameter in the Y-axis direction (the minor diameter X2) so that the length of the electron beam EB in the Z-axis direction is greater than its length in the Y-axis direction. Therefore, by adjusting the amount of current flowing through the coil 43d, the aspect ratio can be selectively adjusted. As an example, the aspect ratio of the major diameter X1 to the minor diameter X2 is adjusted to "10:1".

[0036] The exhaust section 5 includes a vacuum pump 5a (a first vacuum pump) and a vacuum pump 5b (a second vacuum pump). The frame 6 is provided with an exhaust flow path E1 (a first exhaust flow path) for vacuum exhausting the space within the frame 6 (i.e., the internal space S1 defined by the frame 6 and the frame 44 of the magnetic lens 4). The vacuum pump 5b is connected to the internal space S1 via the exhaust flow path E1. The frame 7 is provided with an exhaust flow path E2 (a second exhaust flow path) for vacuum exhausting the space within the frame 7 (i.e., the internal space S2 defined by the frame 7). The vacuum pump 5a is connected to the internal space S2 via the exhaust flow path E2. The vacuum pump 5b vacuum exhausts the internal space S1 via the exhaust flow path E1. The vacuum pump 5a vacuum exhausts the internal space S2 via the exhaust flow path E2. As a result, the internal space S1 and the internal space S2 are maintained in a vacuum state or a partial vacuum state, for example, by removing gas generated in the electron gun or the target. The internal pressure of the internal space S1 is preferably maintained at 10 -4 Partial vacuum below Pa, preferably maintained at 10 -5 The internal pressure of the internal space S2 is preferably maintained at 10 -6 Pa~10 -3 The partial vacuum between Pa. The internal space of the cylindrical tube 9 (the space within the electron passage P) is also vacuum-evacuated by the exhaust unit 5 via the internal space S1 or the internal space S2.

[0037] Furthermore, it may not be Figure 1 The embodiment shown in FIG. 1 does not use two exhaust pumps, namely, the vacuum pump 5a and the vacuum pump 5b, but uses a vacuum pump 5a and a vacuum pump 5b. Figure 8As shown, a structure (X-ray generating device 1A) is adopted in which both the internal space S1 and the internal space S2 can be vacuum-exhausted by a single exhaust pump (here, vacuum pump 5b is used as an example). In some embodiments, the exhaust flow path E1 and the exhaust flow path E2 can be connected by a connecting path E3 located outside the frame 6 and the frame 7. In other examples, the connecting path E3 may also include a through hole, which is continuously provided from the wall of the frame 7 to the wall of the frame 6 in a manner that connects the exhaust flow path E1 and the exhaust flow path E2. Furthermore, either the vacuum pump 5a or the vacuum pump 5b can be used as the single exhaust pump. By using the vacuum pump 5b connected to the exhaust flow path E1 as the exhaust pump, more efficient vacuum exhaust can be achieved.

[0038] In some embodiments, a voltage is applied to the electron gun 2 while the internal spaces S1 and S2 and the electron passage P are evacuated. As a result, an electron beam EB with a circular cross-section is emitted from the electron gun 2. The electron beam EB is focused by the magnetic lens 4 onto the target 31, deformed into an elliptical cross-section, and incident on the rotating target 31. When the electron beam EB enters the target 31, X-rays XR are generated on the target 31. The X-rays XR, having a substantially circular effective focus, are emitted from the X-ray passage aperture 7a toward the exterior of the housing 7.

[0039] like Figure 2 As shown, the cylindrical tube 9 has a configuration in which its diameter changes stepwise along the X-axis. For example, the cylindrical tube 9 includes six cylindrical portions 91 to 96 arranged along the X-axis. Each cylindrical portion 91 to 96 has a constant diameter along the X-axis. The outer diameter of the cylindrical tube 9 does not necessarily change synchronously with its inner diameter. In other words, the outer diameter of the cylindrical tube 9 can be constant.

[0040] The cylindrical portion 91 (first cylindrical portion) includes a first end 9a of the cylindrical tube 9 on the electron gun 2 side. The cylindrical portion 91 extends from the first end 9a to a second end 91a, surrounded by the portion of the coil 42a on the electron gun 2 side of the boundary portion 9c. The first end 92a of the cylindrical portion 92 (second cylindrical portion) is connected to the second end 91a of the cylindrical portion 91 on the target 31 side. In some embodiments, the cylindrical portion 92 extends from the second end 91a of the cylindrical portion 91 to the second end 92b of the second cylindrical portion 92, which is located slightly closer to the target 31 side than the pole piece 42b. For example, the second end 92b of the second cylindrical portion 92 may be located between the pole piece 42b and the target 31 along the X-axis. Furthermore, the first end 93a of the cylindrical portion 93 (third cylindrical portion) is connected to the second end 92b of the cylindrical portion 92 on the target 31 side.

[0041] The cylindrical portion 93 extends from the second end 92b of the cylindrical portion 92 to the second end 93b of the cylindrical portion 93 surrounded by the magnetic quadrupole lens 43. The first end of the cylindrical portion 94 (the fourth cylindrical portion) is connected to the second end 93b of the cylindrical portion 93 on the target 31 side. The cylindrical portion 94 extends from the second end 93b of the cylindrical portion 93 to the frame 7 side of the wall portion 44c.

[0042] The cylindrical portion 95 (the fifth cylindrical portion) and the cylindrical portion 96 (the sixth cylindrical portion) pass through the interior of the wall portion 71 of the frame 7. The wall portion 71 is arranged at a position opposite to the target 31 and extends in a manner intersecting the X-axis direction. The cylindrical portion 95 is connected to the second end portion of the cylindrical portion 94 on the target 31 side. The cylindrical portion 95 extends from the end portion of the cylindrical portion 94 to the middle portion of the interior of the wall portion 71. The cylindrical portion 96 is connected to the end portion of the cylindrical portion 95 on the target 31 side at the middle portion of the interior of the wall portion 71. The cylindrical portion 96 extends from the end portion of the cylindrical portion 95 to the second end portion 9b of the cylindrical tube 9 on the target 31 side. Furthermore, as Figure 2 As shown, the exemplary X-ray passage hole 7a is provided in a wall portion 72, which is connected to the wall portion 71 and extends so as to intersect the Z-axis direction. The X-ray passage hole 7a penetrates the wall portion 72 along the Z-axis direction.

[0043] In some embodiments, if the diameters of the cylindrical portions 91 to 96 are represented by d1 to d6, the relationship "d2 > d3 > d1 > d4 > d5 > d6" holds. For example, diameter d1 is 6 to 12 mm, diameter d2 is 10 to 14 mm, diameter d3 is 8 to 12 mm, diameter d4 is 4 to 6 mm, diameter d5 is 4 to 6 mm, and diameter d6 is 0.5 to 4 mm.

[0044] At least a portion of the cylindrical portion 91 and the cylindrical portion 92 are located closer to the electron gun 2 than the portion of the electron passage P surrounded by the pole piece 42b of the magnetic focusing lens 42 (particularly, the gap between the yoke 42c and the yoke 42d). In some embodiments, at least a portion of the cylindrical portion 91 and the cylindrical portion 92 constitute "a portion of the electron passage P closer to the electron gun 2 than the portion surrounded by the pole piece 42b of the magnetic focusing lens 42" (hereinafter referred to as the "first cylindrical portion"). Furthermore, as described above, the diameter d2 of the cylindrical portion 92 is larger than the diameter d1 of the cylindrical portion 91 (d2 > d1). In other words, within the first cylindrical portion, at least a portion of the cylindrical portion 92 constitutes an expanded diameter portion, which expands toward the target 31.

[0045] The cylindrical portion 96 includes the end portion 9b on the target 31 side of the electron passage path P. Further, the diameter d6 of the cylindrical portion 96 is smaller than the diameter d5 of the cylindrical portion 95 (d6 < d5). That is, the diameter of the cylindrical portion 96 is reduced compared to the diameter of the cylindrical portion 95 adjacent on the electron gun 2 side, and the cylindrical portion 96 constitutes a diameter-reducing portion that reduces in diameter toward the target 31 side. In several embodiments, the diameter d2 of the cylindrical portion 92 is the maximum diameter of the cylindrical tube 9, and the diameter is gradually reduced from the cylindrical portion 92 toward the target 31 side. Therefore, it can be understood that the above-described diameter-reducing portion is constituted by the portion including the cylindrical portions 93 to 96.

[0046] In several embodiments, the size of the electron beam EB is adjusted by the magnetic focusing lens 42 disposed at a stage rearward of the electron gun 2, and the cross-sectional shape of the electron beam EB is deformed into an elliptical shape by the magnetic quadrupole lens 43 disposed at a stage rearward of the magnetic focusing lens 42. Therefore, the adjustment of the size of the electron beam EB and the adjustment of the cross-sectional shape can be performed independently of each other.

[0047] Figure 4 of (A) includes Figure 1 and Figure 2 a schematic view of a structural example of the magnetic focusing lens 42 and the magnetic quadrupole lens 43 shown. Figure 4 of (B) is a schematic view of the structure (doublet lens) of the comparative example. Figure 4 of (A) and (B) are diagrams schematically showing an example of an optical system acting on the electron beam EB between the cathode C (electron gun 2) and the target 31. In Figure 4 the structure of the comparative example shown in (B) of, the size and aspect ratio of the cross-sectional shape of the electron beam are adjusted by combining two magnetic quadrupole lenses in which the surface acting as a concave lens and the surface acting as a convex lens are interchanged with each other. In Figure 4 the comparative example of (B), the lens that determines the size of the cross-sectional shape of the electron beam and the lens that determines the aspect ratio are not independent of each other. Therefore, it is necessary to reset the size and aspect ratio simultaneously by combining two magnetic quadrupole lenses. Therefore, the adjustment of the focus size and the focus shape is complicated. In contrast, in Figure 4 the structure of the embodiment shown in (A) of, the size of the cross-sectional shape of the electron beam EB is adjusted by the magnetic focusing lens 42 in the front stage. That is, by the magnetic focusing lens 42, the cross-sectional shape of the electron beam EB is narrowed to a certain size. Thereafter, the aspect ratio of the cross-sectional shape of the electron beam EB is adjusted by the magnetic quadrupole lens 43 in the rear stage. In this way, in Figure 4 the structure of the embodiment of (A), the lens (magnetic focusing lens 42) that determines the size of the cross-sectional shape of the electron beam EB and the lens (magnetic quadrupole lens 43) that determines the aspect ratio are independent of each other. Therefore, the adjustment of the focus size and the focus shape can be easily and flexibly performed.

[0048] Furthermore, while the electron beam EB passing through the magnetic focusing lens 42 rotates about an axis along the X-axis, the cross-sectional shape of the electron beam EB emitted by the electron gun 2 is circular. Therefore, the cross-sectional shape of the electron beam EB that passes through the magnetic focusing lens 42 and reaches the magnetic quadrupole lens 43 is constant (circular) regardless of the amount of rotation of the electron beam EB within the magnetic focusing lens 42. Thus, within the magnetic quadrupole lens 43, the cross-sectional shape F1 (cross-sectional shape along the YZ plane) of the electron beam EB can be consistently and reliably shaped into an elliptical shape having a major diameter X1 along the Z-direction and a minor diameter X2 along the Y-axis. This makes it possible to easily and flexibly adjust the aspect ratio and size of the cross-sectional shape of the electron beam EB.

[0049] The performance of an X-ray generator 1 according to an embodiment of the present invention, which includes an electron gun 2 and a magnetic lens 4, was evaluated through experiments. A high voltage was applied to the electron gun 2, and the target 31 was set to ground potential. At the desired output (voltage applied to the cathode C), X-rays XR with an effective focal spot size of "40 μm × 40 μm" were obtained. Even when the focal spot size varied during 1000 hours of operation, the above-described effective focal spot size could be easily restored simply by adjusting the current flowing through the coil 43d of the magnetic quadrupole lens 43, without changing the operating conditions on the cathode C side. As described above, according to the X-ray generator 1, it was confirmed that the effective focal spot size of the X-rays XR could be easily corrected in response to dynamic changes simply by adjusting the current flowing through the coil 43d.

[0050] In several embodiments, such as Figure 5 As shown, the target 31 has an electron incident surface 31a on which the electron beam EB is incident. The electron incident surface 31a is tilted relative to the X-axis and Z-axis directions. Furthermore, the cross-sectional shape F1 (i.e., the ratio of the major diameter X1 to the minor diameter X2) of the electron beam EB after being deformed into an elliptical shape by the magnetic quadrupole lens 43, and the tilt angle of the electron incident surface 31a relative to the X-axis and Y-axis directions are adjusted so that the focal point shape F2 of the X-rays XR observed from the extraction direction (Z-axis direction) of the X-rays XR becomes approximately circular. In some embodiments, by adjusting the tilt angle of the electron incident surface 31a of the target 31 and the shaping conditions (aspect ratio) performed by the magnetic quadrupole lens 43, the shape of the focal point (effective focal point) of the extracted X-rays XR can be set to a approximately circular shape. As a result, an appropriate inspection image can be obtained in X-ray inspection, etc. using the X-rays XR generated by the X-ray generator 1.

[0051] In several embodiments, such as Figure 2As shown, the length of the magnetic focusing lens 42 along the X-axis direction is longer than the length of the magnetic quadrupole lens 43 along the X-axis direction. Here, the "length of the magnetic focusing lens 42 along the X-axis direction" refers to the total length of the yoke 42c surrounding the coil 42a. In some embodiments, it is easier to ensure the number of turns of the coil 42a of the magnetic focusing lens 42. As a result, by generating a relatively large magnetic field by the magnetic focusing lens 42, the reduction rate is further increased, thereby effectively focusing the electron beam EB to a smaller size. Furthermore, in order to reduce the size of the electron beam EB incident on the electron incident surface 31a of the target 31, the distance from the electron gun 2 to the center of the lens formed by the magnetic focusing lens 42 (the portion where the pole piece 42b is provided) can be lengthened.

[0052] In addition, the inner diameter D of the pole piece 42b of the magnetic focusing lens 42 is larger than the inner diameter d of the magnetic quadrupole lens 43 (refer to Figure 3 In some embodiments, by making the inner diameter D of the pole piece 42b of the magnetic focusing lens 42 relatively large, the spherical aberration of the lens formed by the magnetic focusing lens 42 can be reduced. Furthermore, by making the inner diameter d of the magnetic quadrupole lens 43 relatively small, the number of turns of the coil 43d of the magnetic quadrupole lens 43 and the amount of current flowing through the coil 43d can be reduced. As a result, the heat generated by the magnetic quadrupole lens 43 can be suppressed.

[0053] The X-ray generator 1 also includes a cylindrical tube 9 extending along the X-axis and forming an electron passage P for the electron beam EB. Furthermore, the magnetic focusing lens 42 and the magnetic quadrupole lens 43 are directly or indirectly connected to the cylindrical tube 9. In some embodiments, the magnetic focusing lens 42 and the magnetic quadrupole lens 43 can be positioned or mounted using the cylindrical tube 9 as a reference. This allows the central axes of the magnetic focusing lens 42 and the magnetic quadrupole lens 43 to be precisely aligned on the same axis. As a result, deformation of the outline (cross-sectional shape) of the electron beam EB after passing through the magnetic focusing lens 42 and the magnetic quadrupole lens 43 can be suppressed.

[0054] The X-ray generator 1 also includes a deflection coil 41. In some embodiments, as described above, the angular offset between the emission axis of the electron beam EB emitted from the electron gun 2 and the central axes of the magnetic focusing lens 42 and the magnetic quadrupole lens 43 can be appropriately corrected. Furthermore, the deflection coil 41 is disposed between the electron gun 2 and the magnetic focusing lens 42. In some embodiments, the direction of travel of the electron beam EB can be appropriately adjusted before the electron beam EB passes through the magnetic focusing lens 42 and the magnetic quadrupole lens 43. As a result, the cross-sectional shape of the electron beam EB incident on the target 31 can be maintained at a desired elliptical shape.

[0055] In the X-ray generator 1, an electron passage P is formed, extending through the housing 6 that houses the cathode C (electron gun 2) and the housing 7 that houses the target 31. Furthermore, the portion of the electron passage P that includes the end portion on the target 31 side (end portion 9b of the cylindrical tube 9) tapers in diameter toward the target 31. In some embodiments, the cylindrical portion 96 (or cylindrical portions 93 to 96) forms a reduced diameter portion that tapers toward the target 31. This makes it difficult for reflected electrons generated within the housing 7 by the electron beam EB incident on the target 31 to reach the housing 6 via the electron passage P. As a result, deterioration of the cathode C caused by reflected electrons emitted from the target 31 can be suppressed or prevented. The term "reflected electrons" refers to electrons in the electron beam EB incident on the target 31 that are not absorbed by the target 31 and are reflected therefrom.

[0056] When the electron beam EB is emitted from the cathode C, gas is generated by the electron gun 2. Gas may remain in the space containing the cathode C. In addition, gas (for example, gaseous byproducts such as H2, H2O, N2, CO, CO2, CH4, Ar, etc.) is generated in the frame 7 due to the collision of electrons with the target 31. As a result, electrons may be reflected from the surface of the target 31. In some embodiments, since the entrance (i.e., the end 9b) on the target 31 side of the electron passage path P is narrowed, less gas is attracted toward the frame 6 side (i.e., the internal space S1) through the electron passage path P, and thus less gas is discharged from the exhaust flow path E1 provided in the frame 6. Therefore, in the X-ray generating device 1, the exhaust path (exhaust flow path E2) for the above-mentioned gas is provided in the frame 7 itself. As a result, vacuum exhaust in each frame 6 and 7 can be appropriately performed, and degradation of the cathode C due to reflected electrons can be suppressed or prevented.

[0057] Furthermore, the portion of the electron passage P closer to the electron gun 2 than the portion surrounded by the pole piece 42b of the magnetic focusing lens 42 (the aforementioned first cylindrical portion) has an expanded diameter portion (at least a portion of the cylindrical portion 92) whose diameter increases toward the target 31. In some embodiments, even if reflected electrons enter the electron passage P from the end 9b of the electron passage P on the target 31 side, the expanded diameter portion that increases toward the target 31 (i.e., the portion that decreases toward the cathode C) can suppress the reflected electrons from traveling through the electron passage P toward the cathode C. Furthermore, the electron beam EB bound for the target 31 can be effectively suppressed from colliding with the inner wall of the electron passage P (the inner surface of the cylindrical tube 9).

[0058] Furthermore, the diameter-enlarged portion of the cylindrical tube 9, which extends from the electron gun 2 side toward the target 31 side, includes a portion (i.e., the boundary between the cylindrical portion 91 and the cylindrical portion 92) that discontinuously changes from a portion having a diameter d1 (first diameter) (i.e., the cylindrical portion 91) toward a portion having a diameter d2 (second diameter) larger than the diameter d1 (i.e., the cylindrical portion 92). In some embodiments, the diameter of the cylindrical tube 9 changes in a stepwise manner at the boundary between the cylindrical portion 91 and the cylindrical portion 92. The boundary portion 9c is formed by an annular wall having an inner diameter of the diameter d1 and an outer diameter of the diameter d2 (see FIG. 1 ). Figure 2 In some embodiments, even if there are reflected electrons traveling from the target 31 toward the electron gun 2 within the electron passage P, the reflected electrons can be caused to collide with the boundary portion 9c. This can more effectively suppress or prevent the reflected electrons from moving toward the cathode C.

[0059] Furthermore, the diameter of the portion of the electron passage P surrounded by the pole piece 42b of the magnetic focusing lens 42 (diameter d2 of the cylindrical portion 92) is greater than the diameter of the remaining portion of the electron passage P. In other words, the electron passage P has its maximum diameter in the portion surrounded by the pole piece 42b of the magnetic focusing lens 42. In some embodiments, by increasing the diameter of the portion where the electron beam EB emitted from the electron gun 2 diverges more (i.e., the portion surrounded by the pole piece 42b) to be greater than the diameter of the remaining portion, the electron beam EB directed toward the target 31 can be effectively suppressed from colliding with the inner wall of the electron passage P (the inner surface of the cylindrical tube 9).

[0060] Furthermore, the exhaust flow path E1 communicates with the exhaust flow path E2. Furthermore, the exhaust unit 5 evacuates the interior of the housing 6 via the exhaust flow path E1 and the interior of the housing 7 via the exhaust flow path E2. In some embodiments, the shared exhaust unit 5 can be used to evacuate both the internal space S1 within the housing 6 and the internal space S2 within the housing 7, thereby miniaturizing the X-ray generator 1.

[0061] It should be understood that all aspects, advantages, and features described in this specification are not necessarily achieved by, or included in, any specific embodiment. In this specification, various embodiments are described, but it should be clear that other embodiments including different materials and shapes may also be adopted.

[0062] For example, if the emission axis of the electron beam EB from the electron gun 2 is accurately aligned with the central axis of the magnetic focusing lens 42, the deflection coil 41 can be omitted. Alternatively, the deflection coil 41 can be disposed between the magnetic focusing lens 42 and the magnetic quadrupole lens 43, or between the magnetic quadrupole lens 43 and the target 31.

[0063] The shape of the electron passage path P (cylindrical tube 9) can have a single diameter throughout the entire structure. In addition, the electron passage path P can be formed by a single cylindrical tube 9. In other examples, the cylindrical tube 9 can be provided only in the frame 6, and the electron passage path P passing through the frame 7 can be formed by a through-hole provided in the wall portion 71 of the frame 7. In addition, the cylindrical tube 9 can be omitted and the electron passage path P can be formed by the through-hole of the tubular member 10 and the through-holes provided in the frame 44 and the frame 7.

[0064] Figure 6 The first variation of the cylindrical tube (cylindrical tube 9A) is shown. In some embodiments, the cylindrical tube 9A has cylindrical portions 91A to 93A instead of the cylindrical portions 91 to 96. Figure 2 The cylindrical tube 9 shown is different. The cylindrical portion 91A extends from the end 9a of the cylindrical tube 9 to the position of the coil 42a surrounded by the electron gun 2 side. The cylindrical portion 91A has a conical shape. For example, the diameter of the cylindrical portion 91A gradually increases from the diameter d1 to the diameter d2 from the end 9a toward the target 31 side. The cylindrical portion 92A extends from the end of the cylindrical portion 91A on the target 31 side to a position slightly closer to the target 31 side than the pole piece 42b. The cylindrical portion 92A has a certain diameter (diameter d2). The cylindrical portion 93A extends from the end of the cylindrical portion 92A on the target 31 side to the end 9b of the cylindrical tube 9. The cylindrical portion 93A has a conical shape. For example, the diameter of the cylindrical portion 93A gradually decreases from the diameter d2 to the diameter d6 from the end of the cylindrical portion 92A toward the target 31 side. In the cylindrical tube 9A, the cylindrical portion 91A corresponds to the diameter expansion portion, and the cylindrical portion 93A corresponds to the diameter reduction portion.

[0065] Figure 7 The second variation of the cylindrical tube (cylindrical tube 9B) is shown. In some embodiments, the cylindrical tube 9B has cylindrical portions 91B and 92B instead of the cylindrical portions 91 to 96. Figure 2 The cylindrical tube 9 shown is different. The cylindrical portion 91B extends from the end 9a of the cylindrical tube 9 to a position surrounded by the pole piece 42b. The cylindrical portion 91B has a tapered shape. For example, the diameter of the cylindrical portion 91B gradually increases from the diameter d1 to the diameter d2 from the end 9a toward the target 31 side. The cylindrical portion 92B extends from the end of the cylindrical portion 91B on the target 31 side to the end 9b of the cylindrical tube 9. The cylindrical portion 92B has a tapered shape. In some embodiments, the diameter of the cylindrical portion 92B gradually decreases from the diameter d2 to the diameter d6 from the end of the cylindrical portion 91B toward the target 31 side. In the cylindrical tube 9B, the cylindrical portion 91B corresponds to the diameter-expanding portion, and the cylindrical portion 92B corresponds to the diameter-reducing portion.

[0066] In some embodiments, the reduced diameter portion and the expanded diameter portion of the cylindrical tube (the path through which electrons pass) may not be formed in a stepped (non-continuous) manner as in cylindrical tube 9, but may be formed in a tapered shape as in cylindrical tubes 9A and 9B. Alternatively, as in cylindrical tube 9B, the cylindrical tube may consist solely of a tapered portion. Furthermore, the cylindrical tube may have both a portion that changes in diameter in a stepped manner and a portion that changes in diameter in a tapered manner. For example, the expanded diameter portion may be tapered as in cylindrical tube 9A, while the reduced diameter portion may be stepped as in cylindrical tube 9.

[0067] Furthermore, the target does not need to be a rotating anode. In some embodiments, the target may not rotate, and the electron beam EB may always be incident on the same position on the target. However, by using the target as a rotating anode, the local load on the target caused by the electron beam EB can be reduced. As a result, the amount of the electron beam EB can be increased, and the amount of X-rays XR emitted from the target can be increased.

[0068] In some embodiments, the electron gun 2 may be configured to emit an electron beam EB having a circular cross-sectional shape. In other examples, the electron gun 2 may be configured to emit an electron beam having a cross-sectional shape other than a circular shape.

[0069] [Note]

[0070] The present disclosure includes the following structures.

[0071] [Structure 1]

[0072] The first exhaust flow path (exhaust flow path E1 ) and the second exhaust flow path (exhaust flow path E2 ) communicate with each other.

[0073] [Structure 2]

[0074] The exhaust system includes a first vacuum exhaust pump (vacuum pump 5b) communicating with the first exhaust flow path (exhaust flow path E1) and a second vacuum exhaust pump (vacuum pump 5a) communicating with the second exhaust flow path (exhaust flow path E2).

[0075] [Structure 3]

[0076] The exhaust system includes one or more pumps (vacuum pumps 5a, 5b) connected to the first exhaust flow path (exhaust flow path E1) and the second exhaust flow path (exhaust flow path E2). The exhaust system is configured to remove gaseous byproducts from the first internal space (internal space S1) and the second internal space (internal space S2).

[0077] [Structure 4]

[0078] While the electron gun 2 is emitting the electron beam EB, gaseous byproducts in the first internal space (internal space S1 ) and the second internal space (internal space S2 ) are removed by the exhaust system.

[0079] [Structure 5]

[0080] At least a portion of the electron gun 2 is located in the first internal space (internal space S1 ), and at least a portion of the target 31 is located in the second internal space (internal space S2 ).

[0081] [Structure 6]

[0082] The X-ray generating device 1 includes: an electron gun 2, which is configured to emit an electron beam EB and is at least partially arranged in a first internal space (internal space S1) within a first housing (housing 6); a target 31 for the electron beam EB, which is at least partially arranged in a second internal space (internal space S2) within a second housing (housing 7); an electron passage P, which is an electron passage P passing between the first internal space (internal space S1) and the second internal space (internal space S2), and has a first end 9a located in the first internal space (internal space S1) and a second end 9b located in the second internal space (internal space S2), and the second end 9b has a diameter-reduced portion (for example, cylindrical portions 93 to 96) that is reduced in diameter toward the target 31; and an exhaust system that evacuates both the first internal space and the second internal space.

[0083] [Structure 7]

[0084] The first end 9a of the electron passage P has an expanded diameter portion (e.g., the end of the cylindrical portion 92 on the cylindrical portion 91 side) that expands toward the target 31. The expanded diameter portion gradually expands from a first diameter (e.g., diameter d1 of the cylindrical portion 91) to a second diameter (e.g., diameter d2 of the cylindrical portion 92) that is larger than the first diameter. The expanded diameter portion forms an annular wall (boundary portion 9c) having the first diameter as its inner diameter and the second diameter as its outer diameter.

[0085] [Structure 8]

[0086] The annular wall (boundary portion 9c) is opposite to the target 31 and is constructed to reduce the number of reflected electrons from the electron gun 2 that reach the first internal space (internal space S1) through the electron passage path P, and to collide with the reflected electrons emitted from the second internal space (internal space S2) when the electron beam EB is incident on the target 31.

[0087] [Structure 9]

[0088] The minimum diameter of the expanded diameter portion at the first end 9a of the electron passage P (for example, the diameter d1 of the cylindrical portion 91) is larger than the minimum diameter of the reduced diameter portion at the second end 9b of the electron passage P (for example, the diameter d6 of the cylindrical portion 96).

[0089] [Structure 10]

[0090] The electron passage P includes an intermediate portion (eg, cylindrical portion 92 ) located between the first end portion 9 a and the second end portion 9 b . The portion of the electron passage P having the largest diameter is located in the intermediate portion.

[0091] [Structure 11]

[0092] Electron passage P comprises three or more cylindrical sections, including: a first cylindrical section (e.g., cylindrical section 91) having a first diameter at first end 9a; a second cylindrical section (e.g., cylindrical sections 93-96) having a reduced diameter portion at second end 9b that decreases toward a second diameter; and an intermediate cylindrical section (e.g., cylindrical section 92) located between the first and second cylindrical sections and having an intermediate diameter. The first diameter (e.g., diameter d1 of cylindrical section 91) is greater than the second diameter (e.g., diameter d6 of cylindrical section 96), and the intermediate diameter (e.g., diameter d2 of cylindrical section 92) is greater than the first diameter.

Claims

1. An X-ray generating device, wherein: have: an electron gun having a cathode for emitting an electron beam; a first frame housing the electron gun; a target on which the electron beam emitted from the electron gun is incident; a second frame housing the target; an electron passage, which is provided across the first frame and the second frame, and allows the electron beam to pass from the first internal space of the first frame to the second internal space of the second frame, and the electron passage has a diameter-reduced portion that is narrowed toward the target diameter; a first exhaust flow path for vacuum exhausting the first internal space in the first frame; a second exhaust flow path for vacuum exhausting the second internal space in the second frame; a magnetic focusing lens arranged to surround a first region of the electron passage path at a rear portion of the electron gun, and to focus the electron beam; a deflection yoke disposed between the electron gun and the magnetic focusing lens so as to surround a second region of the electron passage, and configured to adjust a traveling direction of the electron beam; and A magnetic quadrupole lens is arranged in a manner surrounding a third region of the electron passage path at the rear stage of the magnetic focusing lens, thereby deforming the shape of the electron beam. The maximum diameter of the first region of the electron passage path is larger than both the maximum diameter of the second region of the electron passage path and the maximum diameter of the third region of the electron passage path.

2. The X-ray generating device according to claim 1, wherein: The electron passage has an expanded diameter portion located between the electron gun and a pole piece of the magnetic focusing lens and expanding toward the target diameter.

3. The X-ray generating device according to claim 2, wherein: The expanded diameter portion discontinuously changes from a first diameter to a second diameter that is larger than the first diameter.

4. The X-ray generating device according to claim 1, wherein: The diameter of the region of the electron passage path surrounded by the pole piece of the magnetic focusing lens is equal to the maximum diameter of the electron passage path.

5. The X-ray generating device according to claim 1, wherein: The system further includes an exhaust system for vacuum-exhausting the first internal space of the first housing through the first exhaust flow path and vacuum-exhausting the second internal space of the second housing through the second exhaust flow path.

6. The X-ray generating device according to claim 5, wherein: The first exhaust flow path communicates with the second exhaust flow path.

7. The X-ray generating device according to claim 5, wherein: The exhaust system includes a first vacuum exhaust pump communicating with the first exhaust flow path and a second vacuum exhaust pump communicating with the second exhaust flow path.

8. The X-ray generating device according to claim 5, wherein: The exhaust system includes: one or more pumps communicating with the first exhaust flow path and the second exhaust flow path; The exhaust system is configured to remove gaseous byproducts from the first internal space and the second internal space.

9. The X-ray generating device according to claim 8, wherein: While the electron gun emits the electron beam, the gas byproducts in the first internal space and the second internal space are removed by the exhaust system.

10. The X-ray generating device according to claim 1, wherein: At least a portion of the electron gun is located in the first internal space. At least a portion of the target is located in the second internal space.

11. An X-ray generating device, wherein: have: an electron gun configured to emit an electron beam and at least partially disposed within the first internal space within the first housing; The target of the electron beam is at least partially disposed in the second internal space within the second frame; an electron passage path passing between the first internal space and the second internal space, having a first end located in the first internal space and a second end located in the second internal space, the second end having a diameter-reduced portion that is reduced toward the target diameter; an exhaust system for vacuum exhausting both the first internal space and the second internal space; a magnetic focusing lens arranged to surround a first region of the electron passage path at a rear portion of the electron gun, and to focus the electron beam; a deflection yoke disposed between the electron gun and the magnetic focusing lens so as to surround a second region of the electron passage, and configured to adjust a traveling direction of the electron beam; and A magnetic quadrupole lens is arranged in a manner surrounding a third region of the electron passage path at the rear stage of the magnetic focusing lens, thereby deforming the shape of the electron beam. The maximum diameter of the first region of the electron passage path is larger than both the maximum diameter of the second region of the electron passage path and the maximum diameter of the third region of the electron passage path.

12. The X-ray generating device according to claim 11, wherein: The device further comprises: a first exhaust flow path for vacuum-exhausting the first internal space; and The second exhaust flow path is configured to vacuum-exhaust the second internal space.

13. The X-ray generating device according to claim 12, wherein: The first exhaust flow path communicates with the second exhaust flow path.

14. The X-ray generating device according to claim 12, wherein: The exhaust system includes: one or more pumps communicating with the first exhaust flow path and the second exhaust flow path; The exhaust system is configured to remove gaseous byproducts from the first internal space and the second internal space.

15. The X-ray generating device according to claim 14, wherein: While the electron gun emits the electron beam, the gas byproducts in the first internal space and the second internal space are removed by the exhaust system.

16. The X-ray generating device according to claim 11, wherein: The first end portion of the electron passage has a diameter-enlarged portion that is enlarged toward the target diameter. The diameter-enlarged portion is gradually enlarged from a first diameter to a second diameter larger than the first diameter. The diameter-enlarged portion forms an annular wall having the first diameter as an inner diameter and the second diameter as an outer diameter.

17. The X-ray generating device according to claim 16, wherein: The annular wall faces the target and is configured to reduce the number of reflected electrons from the electron gun that pass through the electron passage and reach the first internal space, and to collide with the reflected electrons emitted from the second internal space when the electron beam is incident on the target.

18. The X-ray generating device according to claim 16, wherein: The minimum diameter of the expanded diameter portion at the first end portion of the electron passage is larger than the minimum diameter of the reduced diameter portion at the second end portion of the electron passage.

19. The X-ray generating device according to claim 16, wherein: The electron passage includes: an intermediate portion located between the first end portion and the second end portion; The portion of the electron passage path having the largest diameter is located in the middle portion.

20. The X-ray generating device according to claim 11, wherein: The electron passage has three or more cylindrical portions including the following parts: a first cylindrical portion having a first diameter at the first end portion; a second cylindrical portion having a diameter-reduced portion at the second end portion that is reduced in diameter toward a second diameter; and an intermediate cylindrical portion located between the first cylindrical portion and the second cylindrical portion and having an intermediate diameter. The first diameter is larger than the second diameter, The intermediate diameter is larger than the first diameter.

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