Electron beam generator and X-ray generating device

Abstract

The electron gun of the electron beam generator of the present invention comprises: a cathode having a front end portion from which an electron beam is emitted; a first electrode receiving a portion including the front end portion of the cathode; and a second electrode surrounding the first electrode when viewed from the direction along the emission axis of the electron beam. The first electrode has a first sidewall surrounding the portion including the front end portion about the emission axis. The second electrode has a second sidewall separate from and surrounding the first sidewall. A first opening is provided in the first sidewall, which communicates a first space surrounded by the first sidewall and a second space between the first sidewall and the second sidewall. A second opening is provided in the second electrode, which opens in the direction along the emission axis in such a way that it communicates the second space with an external space.

Description

Technical Field

[0001] One aspect of this disclosure relates to an electron beam generator and an X-ray generating apparatus. Background Technology

[0002] X-ray generating devices that direct an electron beam toward a target are known. For example, Patent Document 1 discloses the structure of an electron gun in which the cathode is housed in a Wehnelt electrode (grid electrode).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2015-041585 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] The Veneret electrode has an opening for the electron beam to pass through. The cathode is consumed by the gas remaining in the space containing the cathode within the grid electrode.

[0008] This specification discloses an example of an electron beam generator and an X-ray generating apparatus that includes a cathode housing space capable of efficient vacuum degassing.

[0009] Technical means to solve the problem

[0010] An exemplary electron gun (electron beam generator) includes: a cathode having a front end from which an electron beam is emitted; a first electrode receiving the front end of the cathode; and a second electrode surrounding the first electrode when viewed from the direction along the emission axis of the electron beam. The first electrode has a first sidewall surrounding the front end about the emission axis. The second electrode has a second sidewall separate from and surrounding the first sidewall. A first opening is provided in the first sidewall, which communicates a first space surrounded by the first sidewall and a second space between the first and second sidewalls. A second opening is provided in the second electrode, which opens in the direction along the emission axis in such a way that it communicates the second space with an external space.

[0011] In several embodiments, a first space within the first electrode (i.e., a cathode housing space containing the cathode) communicates with a second space between the first and second sidewalls via a first opening provided on the first sidewall. Furthermore, the second space communicates with an external space via a second opening provided on the second electrode. Thus, gas remaining in the cathode housing space is discharged into the second space through the first opening, and gas discharged into the second space is discharged into the external space through the second opening. Therefore, according to the electron gun described above, vacuum venting of the cathode housing space can be performed efficiently.

[0012] The first opening may have an elongated shape extending circumferentially around the ejection axis in order to allow for vacuum exhaust within the first space.

[0013] Viewed from a direction orthogonal to the emission axis, the second sidewall can cover and conceal the first opening. In several embodiments, structures such as the edge forming the first opening, where there is a large potential difference between the electron gun and the inner wall of the frame housing the electron gun, can be concealed. This suppresses the generation of discharge.

[0014] The electron gun described above may further include a third electrode having a third sidewall that surrounds a support portion supporting the front end of the cathode around the emission axis. A third opening may be provided on the third sidewall to communicate with an external space in the third space surrounded by the third sidewall. In several embodiments, gas remaining in the cathode receiving space (third space) housing the support portion supporting the front end of the cathode may also be discharged to the external space through the third opening.

[0015] The electron gun described above may be provided with a through hole that connects at least one of the first and second spaces to the third space. In several embodiments, the third space is connected to at least one of the first and second spaces for gas exhaust.

[0016] The second sidewall can surround the third sidewall around the emission axis. A fourth opening can be provided on the second sidewall to connect the fourth space between the second and third sidewalls and the external space. The third space can communicate with the external space via the fourth space. In several embodiments, in a configuration where the second sidewall, which is configured as the second electrode, surrounds the third sidewall of the third electrode, gas remaining in the third space can be discharged to the external space via the third opening, the fourth space, and the fourth opening.

[0017] The third and fourth openings can be configured to be non-opposite to each other. By configuring the third and fourth openings so that the third opening is not visible through the fourth opening, the edges of the third opening and other structures with a large potential difference from the inner wall of the frame housing the electron gun can be concealed. This suppresses the generation of discharge.

[0018] An exemplary X-ray generating device includes an electron gun having the structure described above.

[0019] The effects of the invention

[0020] In the embodiments disclosed in this specification, the cathode housing space of an electron gun or other electron beam generator can be evacuated. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of an illustrative X-ray generating device.

[0022] Figure 2 This is a schematic cross-sectional view showing an example of the structure of a magnetic lens in an X-ray generating device.

[0023] Figure 3 This is a front view of an illustrative magnetic quadrupole lens.

[0024] Figure 4 This is a schematic diagram of the structure (doublet lens) of an embodiment and comparative example including a magnetic focusing lens and a magnetic quadrupole lens.

[0025] Figure 5 This is a diagram illustrating an example of the relationship between the cross-sectional shape of the electron beam and the shape of the effective focal point of the X-ray.

[0026] Figure 6 It is a three-dimensional view of an illustrative electron beam generator, such as an electron gun.

[0027] Figure 7 This is a side view of an electron beam generator.

[0028] Figure 8 This is a side view of an electron beam generator.

[0029] Figure 9 This is a cross-sectional view of a portion of an electron beam generator.

[0030] Figure 10 This is a three-dimensional view of the first gate electrode and the first holding electrode.

[0031] Figure 11 It is along Figure 10 A cross-sectional view of the XI-XI line.

[0032] Figure 12 This is a three-dimensional view of the second holding electrode.

[0033] Figure 13 It is along Figure 7 A cross-sectional view of line XIII-XIII in the diagram.

[0034] Figure 14 This is a diagram showing the first variation of a cylindrical tube.

[0035] Figure 15 This is a diagram showing the second variation of the cylindrical tube.

[0036] Figure 16 This is a schematic structural diagram of a modified X-ray generating device. Detailed Implementation

[0037] In the following description, reference is made to the accompanying drawings, and the same or equivalent symbols are used for the same or equivalent elements, and repeated descriptions are omitted.

[0038] like Figure 1 As shown, the exemplary X-ray generating apparatus 1 includes: an electron gun 2, a rotating anode unit 3, a magnetic lens 4, an exhaust section 5, a frame 6 (first frame) defining an internal space S1 for accommodating the electron gun 2, and a frame 7 (second frame) defining an internal space S2 for accommodating the rotating anode unit 3. The frames 6 and 7 can be configured to be detachable from each other, integrally joined together, or integrally formed from the beginning.

[0039] Electron gun 2 emits an electron beam EB. Electron gun 2 has a cathode C that emits the electron beam EB. Cathode C is a circular planar cathode that emits the electron beam EB with a circular cross-sectional shape. The cross-sectional shape of the electron beam EB refers to the cross-sectional shape in a direction perpendicular to the direction parallel to the direction of travel of the electron beam EB, i.e., the X-axis direction (first direction). That is, the cross-sectional shape of the electron beam EB is a shape in the YZ plane. In order to form an electron beam EB with a circular cross-sectional shape, for example, the electron emission surface of cathode C itself can have a circular shape when viewed from a position opposite to the electron emission surface of cathode C (viewed from the X-axis direction).

[0040] The rotating anode unit 3 includes a target 31, a rotating support 32, and a drive unit 33 that drives the rotating support 32 to rotate around a rotation axis A. The target 31 is disposed along the periphery of the flat, frustum-shaped rotating support 32, which is formed around the rotation axis A. The rotation axis A is the central axis of the rotating support 32, and the side surface of the frustum-shaped rotating support 32 has a surface inclined relative to the rotation axis A. Alternatively, the rotating support 32 can be formed as an annular shape around the rotation axis A. The material constituting the target 31 is, for example, heavy metals such as tungsten, silver, rhodium, molybdenum, and their alloys. The rotating support 32 is designed to rotate around the rotation axis A. The material constituting the rotating support 32 is, for example, copper, copper alloys, or other metals. The drive unit 33 has a drive source such as a motor, which drives the rotating support 32 to rotate around the rotation axis A. The target 31 rotates along with the rotating support 32 while receiving an electron beam EB, thereby generating X-rays (XR). X-rays (XR) are emitted from the X-ray through-hole 7a formed in the frame 7 and exit towards the outside of the frame 7. The X-ray through-hole 7a is hermetically sealed by the 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 also be inclined relative to the incident direction of the electron beam EB toward the target 31, extending in a direction intersecting the aforementioned incident direction. The target 31 may be a so-called reflective type, emitting X-rays (XR) in a direction intersecting the direction of travel of the electron beam EB (the incident direction toward the target 31). In several embodiments, the emission direction of the X-rays (XR) is 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 designated as the X-axis direction (first direction), the direction parallel to the emission direction of the X-rays (XR) from the target 31 is designated as the Z-axis direction (second direction), and the direction orthogonal to both the X-axis and Z-axis directions is designated as the Y-axis direction (third direction).

[0041] A 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 sequentially along the X-axis from the electron gun 2 side to the target 31 side. An electron path P is formed between the electron gun 2 and the target 31 for the electron beam EB to pass through. Figure 2 As shown, the electrons can pass through path P via a cylindrical tube 9 (cylindrical portion). The cylindrical tube 9 is a non-magnetic metallic component extending along the X-axis between the electron gun 2 and the target 31. Details regarding additional illustrative structures of the cylindrical tube 9 will be described later.

[0042] 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, the deflection coil 41, magnetic focusing lens 42, and magnetic quadrupole lens 43 are assembled with the cylindrical tube 9 as a reference, so that the central axes of each are precisely aligned on the same axis. Thus, the central axes of each of the deflection coil 41, magnetic focusing lens 42, and magnetic quadrupole lens 43 are aligned with the central axis of the cylindrical tube 9 (the axis parallel to the X-axis).

[0043] A deflection coil 41 is disposed between the electron gun 2 and the magnetic focusing lens 42. The deflection coil 41 is configured to surround the electron path P. For example, the deflection coil 41 is indirectly connected to the cylindrical tube 9 via a cylindrical member 10. The cylindrical member 10 is a non-magnetic metal member that extends coaxially with the cylindrical tube 9. The cylindrical member 10 is configured to cover the outer periphery of the cylindrical tube 9. The deflection coil 41 is located on the target 31 side of the wall portion 44a and on the outer peripheral surface of the cylindrical member 10. The wall portion 44a is part of a frame 44 located opposite the internal space S1 and includes a non-magnetic material. The deflection coil 41 adjusts the travel direction of the electron beam EB emitted from the electron gun 2. The deflection coil 41 may contain one (one group) of deflection coils or two (two groups) of deflection coils. When the deflection coil 41 includes one deflection coil (i.e., the former), the deflection coil 41 can be configured to correct the angular deviation between the emission axis of the electron beam EB emitted from the electron gun 2 and the central axis (parallel to the X-axis) of the magnetic focusing lens 42 and the magnetic quadrupole lens 43. For example, the angular deviation may occur when the emission axis and the central axis intersect at a specific angle. Therefore, by using the deflection coil 41 to change the travel direction of the electron beam EB to the direction along the central axis, the angular deviation can be eliminated. When the deflection coil 41 includes two deflection coils (i.e., the latter), two-dimensional deflection can be performed by the deflection coil 41. Therefore, not only the angular deviation can be corrected, but also the lateral deviation between the emission axis and the central axis (e.g., the emission axis and the central axis are parallel to each other in the X-axis direction and separated in one or both of the Y-axis and Z-axis directions) can be appropriately corrected.

[0044] The magnetic focusing lens 42 is positioned rearward from the electron gun 2 and the deflection coil 41. The magnetic focusing lens 42 focuses the electron beam EB while rotating it about 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 has a coil 42a, pole piece 42b, yoke 42c, and yoke 42d arranged to surround the electron path P. The yoke 42c also functions as a wall 44b of a frame 44 that connects a portion of the outer side of the coil 42a to the cylindrical member 10. The yoke 42d is a cylindrical member that covers the outer periphery 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, the pole piece 42b may also include a notch (gap) between the yoke 42c and the yoke 42d, and a portion of the yoke 42c and the yoke 42d located near the notch. The inner diameter D of the pole piece 42b is equal to the inner diameter of the region adjacent to the gap of the yoke 42c or the yoke 42d. Therefore, the magnetic focusing lens 42 may also be configured to leak the magnetic field of the coil 42a from the pole piece 42b toward the cylindrical tube 9.

[0045] The magnetic quadrupole lens 43 is positioned further back than 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 axis along the Z-axis and a minor axis along the Y-axis. The magnetic quadrupole lens 43 is positioned to surround the electron path P. For example, the magnetic quadrupole lens 43 is indirectly connected to the cylindrical tube 9 via a wall portion 44c of the frame 44. The wall portion 44c is configured to connect to and cover the outer periphery of the cylindrical tube 9. The wall portion 44c is made of a non-magnetic metallic material.

[0046] like Figure 3As shown, the exemplary magnetic quadrupole lens 43 has: an annular magnetic yoke 43a, four cylindrical magnetic yokes 43b disposed on the inner circumferential surface of the magnetic yoke 43a, and a magnetic yoke 43c disposed at the front end of each magnetic yoke 43b. A coil 43d is wound around the magnetic yoke 43b. Each magnetic yoke 43c has a generally semi-circular cross-sectional shape in the YZ plane. The inner diameter d of the magnetic quadrupole lens 43 is the diameter of the inscribed circle at the innermost end of each magnetic yoke 43c. The magnetic quadrupole lens 43 functions as a concave lens in the XZ plane (a plane orthogonal to the Y-axis direction) and as a convex lens in the XY plane (a plane orthogonal to the Z-axis direction). Through the function of the magnetic quadrupole lens 43, the aspect ratio of the diameter (major axis X1) of the electron beam EB along the Z-axis direction to the diameter (minor axis X2) along the Y-axis direction is adjusted such that the length of the electron beam EB along the Z-axis direction is greater than its length along the Y-axis direction. Therefore, the aspect ratio can be selectively adjusted by adjusting the amount of current flowing through coil 43d. As an example, the aspect ratio of the major diameter X1 to the minor diameter X2 is adjusted to "10:1".

[0047] The exhaust section 5 includes a vacuum pump 5a (first vacuum pump) and a vacuum pump 5b (second vacuum pump). In the frame 6, an exhaust flow path E1 (first exhaust flow path) is provided for evacuating 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. In the frame 7, an exhaust flow path E2 (second exhaust flow path) is provided for evacuating 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 evacuates the internal space S1 via the exhaust flow path E1. The vacuum pump 5a evacuates the internal space S2 via the exhaust flow path E2. Thus, the internal spaces S1 and S2 are maintained in a vacuum state or a partial vacuum state, for example, by removing the gas generated in the electron gun or target. The internal pressure of the internal space S1 is preferably maintained at 10. -4 The vacuum below Pa is preferably maintained at 10 Pa. -5 A partial vacuum below Pa. The internal pressure of the internal space S2 is preferably maintained at 10. -6 Pa~10 -3 The partial vacuum between Pa. Regarding the internal space of the cylindrical tube 9 (the space within the electron path P), the vacuum is also exhausted by the exhaust section 5 via the internal space S1 or the internal space S2.

[0048] Furthermore, it may not be like this. Figure 1 Instead of using two exhaust pumps, vacuum pump 5a and vacuum pump 5b, as shown in the diagram, it is as follows: Figure 8As shown, the X-ray generating apparatus 1A employs a configuration where both internal spaces S1 and S2 are evacuated using a single exhaust pump (here, for example, vacuum pump 5b). In several embodiments, exhaust paths E1 and E2 can be connected via a connecting path E3 located outside the frames 6 and 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 toward the wall of the frame 6 in a manner that connects exhaust paths E1 and E2. Furthermore, either vacuum pump 5a or vacuum pump 5b can be used as the single exhaust pump; by using vacuum pump 5b, which is connected to exhaust path E1, as the exhaust pump, more efficient vacuum evacuation can be achieved.

[0049] In several embodiments, a voltage is applied to the electron gun 2 while the internal spaces S1 and S2 and the electron passage path 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 and deformed into an elliptical cross-section shape, and then incident on the rotating target 31. If the electron beam EB is incident on the target 31, X-rays XR are generated on the target 31, and the X-rays XR with an effective focal point shape that is approximately circular are emitted from the X-ray passage hole 7a toward the outside of the frame 7.

[0050] like Figure 2 As shown, the cylindrical tube 9 has a shape in which the diameter varies in stages along the X-axis direction. For example, the cylindrical tube 9 has six cylindrical portions 91 to 96 arranged along the X-axis direction. Each of the cylindrical portions 91 to 96 has a certain diameter along the X-axis direction. The outer diameter of the cylindrical tube 9 may not change synchronously with the inner diameter of the cylindrical tube 9. That is, the outer diameter of the cylindrical tube 9 may be constant.

[0051] The cylindrical portion 91 (first cylindrical portion) includes a first end portion 9a on the electron gun 2 side of the cylindrical tube 9. The cylindrical portion 91 extends from the first end portion 9a to a second end portion 91a of the boundary portion 9c, which is surrounded by the portion on the electron gun 2 side of the coil 42a. The first end portion 92a of the cylindrical portion 92 (second cylindrical portion) is connected to the second end portion 91a on the target 31 side of the cylindrical portion 91. In several embodiments, the cylindrical portion 92 extends from the second end portion 91a of the cylindrical portion 91 to a second end portion 92b of the second cylindrical portion 92 located slightly closer to the target 31 side than the electrode 42b. For example, the second end portion 92b of the second cylindrical portion 92 may be located between the electrode 42b and the target 31 along the X-axis direction. Additionally, the first end portion 93a of the cylindrical portion 93 (third cylindrical portion) is connected to the second end portion 92b on the target 31 side of the cylindrical portion 92.

[0052] 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.

[0053] Cylindrical portion 95 (5th cylindrical portion) and cylindrical portion 96 (6th cylindrical portion) pass through the interior of wall portion 71 of frame 7. Wall portion 71 is positioned opposite target 31 and extends intersecting the X-axis direction. Cylindrical portion 95 is connected to the second end of cylindrical portion 94 on the target 31 side. Cylindrical portion 95 extends from this end of cylindrical portion 94 to a midway point inside wall portion 71. Cylindrical portion 96 is connected to the end of cylindrical portion 95 on the target 31 side at a midway point inside wall portion 71. Cylindrical portion 96 extends from this end of cylindrical portion 95 to the second end 9b of cylindrical tube 9 on the target 31 side. Furthermore, as Figure 2 As shown, an exemplary X-ray through-hole 7a is disposed in wall portion 72, which is connected to wall portion 71 and extends in a manner intersecting the Z-axis direction. The X-ray through-hole 7a penetrates wall portion 72 along the Z-axis direction.

[0054] In several embodiments, if the diameters of each cylindrical portion 91 to 96 are denoted as d1 to d6, then the relationship "d2>d3>d1>d4>d5>d6" holds true. As an 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.

[0055] At least a portion of cylindrical portions 91 and 92, located in the electron passage path P, is closer to the electron gun 2 side than the portion surrounded by the pole piece 42b of the magnetic focusing lens 42 (particularly the gap between the magnetic yoke 42c and the magnetic yoke 42d). In several embodiments, at least a portion of cylindrical portions 91 and 92 constitutes "the portion in the electron passage path P that is closer to the electron gun 2 side than the portion surrounded by the pole piece 42b of the magnetic focusing lens 42" (hereinafter referred to as "the first cylindrical portion"). Moreover, as described above, the diameter d2 of cylindrical portion 92 is larger than the diameter d1 of cylindrical portion 91 (d2>d1). That is, the diameter of cylindrical portion 92 is larger than that of cylindrical portion 91 adjacent to it on the electron gun 2 side. In other words, in the first cylindrical portion, at least a portion of cylindrical portion 92 constitutes a diameter-enlarged portion that expands towards the target 31 side.

[0056] The cylindrical portion 96 includes an end portion 9b on the target 31 side of the electron passage path P. Moreover, 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 to 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-mentioned diameter-reducing portion is constituted by the portion including the cylindrical portions 93 to 96.

[0057] In several embodiments, the size of the electron beam EB is adjusted by the magnetic focusing lens 42 disposed in a later stage than 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 in a later stage than 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.

[0058] Figure 4 of (A) includes Figure 1 and Figure 2 A schematic diagram of a structural example of the magnetic focusing lens 42 and the magnetic quadrupole lens 43 shown. Figure 4 of (B) is a schematic diagram 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 In 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 In the comparative example of (B) of, 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 focus shape is complicated. In contrast, in Figure 4 In 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 later stage. In this way, in Figure 4 In the structure of the embodiment of (A) of, 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 focus shape can be easily and flexibly performed.

[0059] Furthermore, the electron beam EB passing through the magnetic focusing lens 42 rotates about an axis along the X-axis. However, since the cross-sectional shape of the electron beam EB emitted from the electron gun 2 is circular, the cross-sectional shape of the electron beam reaching the magnetic quadrupole lens 43 via the magnetic focusing lens 42 is constant (circular) regardless of the amount of rotation of the electron beam EB within the magnetic focusing lens 42. Therefore, in the magnetic quadrupole lens 43, the cross-sectional shape F1 (the 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 axis X1 along the Z-axis and a minor axis X2 along the Y-axis. Through the above, the aspect ratio and size of the cross-sectional shape of the electron beam EB can be easily and flexibly adjusted.

[0060] The performance of the X-ray generating apparatus 1, equipped with 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. An X-ray XR with an effective focal size of 40 μm × 40 μm was obtained at the desired output (the applied voltage to the cathode C). During 1000 hours of operation, even with changes in the focal size, the aforementioned effective focal size was easily obtained again by adjusting only the current in the coil 43d of the magnetic quadrupole lens 43, without changing the operating conditions on the cathode C side. As described above, the X-ray generating apparatus 1 confirmed that the effective focal size of the X-ray XR can be easily corrected to dynamic changes simply by adjusting the current in the coil 43d.

[0061] 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 axis X1 to the minor axis 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 spot shape F2 of the X-ray XR observed from the extraction direction (Z-axis direction) of the X-ray XR is approximately circular. In several 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 spot (effective focal spot) of the extracted X-ray XR can be set to approximately circular. As a result, appropriate inspection images can be obtained in X-ray inspections using X-ray XR generated by the X-ray generating apparatus 1.

[0062] In several embodiments, such as Figure 2As shown, the length of the magnetic focusing lens 42 along the X-axis is longer than the length of the magnetic quadrupole lens 43 along the X-axis. Here, the "length of the magnetic focusing lens 42 along the X-axis" refers to the total length of the magnetic yoke 42c surrounding the coil 42a. In several embodiments, it is easy 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 with the magnetic focusing lens 42, the reduction ratio is further improved, and thus the electron beam EB can be effectively focused 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 pieces 42b are provided) can be increased.

[0063] 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 several embodiments, by setting the inner diameter D of the pole piece 42b of the magnetic focusing lens 42 to a relatively large value, the spherical aberration of the lens formed by the magnetic focusing lens 42 can be reduced. Furthermore, by setting the inner diameter d of the magnetic quadrupole lens 43 to a relatively small value, 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 generation of the magnetic quadrupole lens 43 can be suppressed.

[0064] Furthermore, the X-ray generating apparatus 1 includes a cylindrical tube 9 that extends along the X-axis, forming an electron passage path P through which the electron beam EB passes. The magnetic focusing lens 42 and the magnetic quadrupole lens 43 are directly or indirectly connected to the cylindrical tube 9. In several embodiments, since the cylindrical tube 9 can be used as a reference for configuring or installing the magnetic focusing lens 42 and the magnetic quadrupole lens 43, their central axes can be precisely aligned coaxially. As a result, deformation of the profile (cross-sectional shape) of the electron beam EB passing through the magnetic focusing lens 42 and the magnetic quadrupole lens 43 can be suppressed.

[0065] Furthermore, the X-ray generating apparatus 1 includes a deflection coil 41. In several embodiments, as described above, appropriate corrections can be made to the angular deviation between the emission axis of the electron beam EB emitted from the electron gun 2 and the central axis of the magnetic focusing lens 42 and the magnetic quadrupole lens 43. Additionally, the deflection coil 41 is disposed between the electron gun 2 and the magnetic focusing lens 42. In several embodiments, the travel direction of the electron beam EB can be appropriately adjusted before it 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 as the desired elliptical shape.

[0066] In the X-ray generating apparatus 1, an electron passage path P is formed throughout the frame 6 that houses the cathode C (electron gun 2) and the frame 7 that houses the target 31. Furthermore, the portion of the electron passage path P that includes the end on the target 31 side (end 9b of the cylindrical tube 9) tapers in diameter towards the target 31 side. In several embodiments, the cylindrical portion 96 (or cylindrical portions 93-96) constitutes a diameter-reducing portion that tapers towards the target 31 side. Therefore, reflected electrons generated within the frame 7 due to the electron beam EB incident on the target 31 are less likely to reach the frame 6 via the electron passage path P. As a result, degradation of the cathode C caused by reflected electrons emitted from the target 31 can be suppressed or prevented. Furthermore, reflected electrons refer to electrons in the electron beam EB incident on the target 31 that are not absorbed by the target 31 and are reflected.

[0067] When the electron beam EB is emitted from the cathode C, gas is generated by the electron gun 2. This gas may remain in the space containing the cathode C. Additionally, gases (e.g., gaseous byproducts such as H2, H2O, N2, CO, CO2, CH4, Ar, etc.) are generated within the frame 7 due to the impact of electrons towards the target 31. Consequently, electrons may be reflected from the surface of the target 31. In several embodiments, because the entrance (i.e., end 9b) on the target 31 side of the electron passage path P narrows, less gas is attracted towards the frame 6 side (i.e., the internal space S1) via the electron passage path P, resulting in less gas being discharged from the exhaust path E1 provided in the frame 6. Therefore, in the X-ray generating apparatus 1, an exhaust path (exhaust path E2) for the aforementioned gas is provided within the frame 7 itself. This allows for appropriate vacuum venting within each frame 6, 7, and suppresses or prevents degradation of the cathode C caused by reflected electrons.

[0068] Furthermore, the portion of the electron passage path P closer to the electron gun 2 side than the portion surrounded by the pole piece 42b of the magnetic focusing lens 42 (the aforementioned first cylindrical portion) has a diameter-enlarging portion (at least a portion of the cylindrical portion 92) that expands towards the target 31 side. In several embodiments, even if reflected electrons enter the electron passage path P from the end 9b on the target 31 side, the diameter-enlarging portion (i.e., the portion whose diameter decreases towards the cathode C side) can suppress the movement of reflected electrons towards the cathode C side via the electron passage path P. Additionally, the collision of the electron beam EB towards the target 31 with the inner wall (inner surface of the cylindrical tube 9) of the electron passage path P can be effectively suppressed.

[0069] Furthermore, from the electron gun 2 side of the cylindrical tube 9 towards the target 31 side, the diameter enlargement portion includes a portion that discontinuously changes from a portion having a diameter d1 (first diameter) (i.e., cylindrical portion 91) towards a portion having a diameter d2 (second diameter) larger than diameter d1 (i.e., cylindrical portion 92) (i.e., the boundary portion between cylindrical portion 91 and cylindrical portion 92). In several embodiments, the diameter of the cylindrical tube 9 changes in a stepped manner at the boundary portion between cylindrical portion 91 and cylindrical portion 92. The boundary portion 9c is formed by an annular wall with an inner diameter of diameter d1 and an outer diameter of diameter d2 (see reference). Figure 2 In several embodiments, even if a reflected electron is present in the electron path P, moving from the target 31 side towards the electron gun 2 side, the reflected electron can be made to collide with the boundary portion 9c. This more effectively suppresses or prevents the reflected electron from moving towards the cathode C side.

[0070] Furthermore, the diameter of the portion of the electron path P surrounded by the pole piece 42b of the magnetic focusing lens 42 (the diameter d2 of the cylindrical portion 92) is greater than or equal to the diameter of the other portions of the electron path P. That is, the portion of the electron path P surrounded by the pole piece 42b of the magnetic focusing lens 42 has the largest diameter. In several embodiments, by increasing the diameter of the portion where the divergence of the electron beam EB emitted from the electron gun 2 is amplified (i.e., the portion surrounded by the pole piece 42b) to be greater than or equal to the diameter of the other portions, the collision between the electron beam EB toward the target 31 and the inner wall (inner surface of the cylindrical tube 9) of the electron path P can be effectively suppressed.

[0071] Furthermore, exhaust flow path E1 is connected to exhaust flow path E2. Moreover, exhaust section 5 exhausts the vacuum inside frame 6 via exhaust flow path E1, and exhausts the vacuum inside frame 7 via exhaust flow path E2. In several embodiments, the vacuum inside both the internal space S1 inside frame 6 and the internal space S2 inside frame 7 can be exhausted through the common exhaust section 5, thus enabling miniaturization of X-ray generating device 1.

[0072] Next, refer to Figures 6 to 13 The detailed structure of electron gun 2, which is an example of an electron beam generator, will be explained. Figures 6 to 13 As shown, the electron gun 2 includes: a cathode C, a first gate electrode 21 (first electrode), a first holding electrode 22, a second gate electrode 23 (second electrode), a second holding electrode 24, a third holding electrode 25 (third electrode), and a stem 26. One or both of the first gate electrode 21 and the second gate electrode 23 can be configured to control the amount of the electron beam EB emitted from the cathode C.

[0073] like Figure 9As shown, the cathode C has a front end C1 and a pair of support pins C2 (support portions). The front end C1 has an electron emission surface EE from which the electron beam EB is emitted. The pair of support pins C2 are electrically connected to and support the front end C1. The pair of support pins C2 may contain a conductive material such as metal. Additionally, the front end C1 may be cylindrical. In several embodiments, the front end face of the front end C1, i.e., the electron emission surface EE, is formed as a circular plane. The electron beam EB is emitted from the electron emission surface EE of the front end C1 along the X-axis direction. The emission axis AX of the electron beam EB is an axis parallel to the X-axis direction, passing through the center of the electron emission surface EE of the front end C1. In several embodiments, the emission axis AX is also the central axis of the electron gun 2. The pair of support pins C2 may be held by a rod portion 26 containing an insulating member such as ceramic. The end of the support pin C2 that is opposite to the front end C1 is electrically connected to an external power supply device via a connecting member or the like disposed in the space S13 surrounded by the third holding electrode 25.

[0074] like Figures 9-11 As shown, the first gate electrode 21 accommodates the front end C1 of the cathode C (at least a portion of the front end C1 side of the pair of support pins C2). The first gate electrode 21 has: a sidewall 211 (first sidewall), a top wall 212, and a bottom wall 213. The material of the first gate electrode 21 may be a high-melting-point metal (e.g., titanium, molybdenum, and alloys containing at least one of them).

[0075] The sidewall 211 surrounds the front end C1 of the cathode C around the emission axis AX. In several embodiments, the sidewall 211 is formed as a cylinder with the emission axis AX as its central axis. An opening 211a (first opening) is provided in the sidewall 211. In addition, a plurality of openings 211a (two in one example) are provided at equal intervals along the circumference around the emission axis AX in the sidewall 211. In several embodiments, two openings 211a are provided opposite to each other with respect to each other across the emission axis AX. Therefore, two openings 211a can be opposite to each other in the Y-axis direction. Each opening 211a has a generally rectangular elongated hole shape extending circumferentially along the emission axis AX. The corners of each opening 211a have a curved surface shape (R-shape). The space S11 (first space) surrounded by the sidewall 211 communicates with the space S12 (the space between the sidewall 211 and the sidewall 231 of the second gate electrode 23) described later via the opening 211a. The space S11 is surrounded by the sidewall 211, the top wall 212, and the bottom wall 213. In several embodiments, the space S11 accommodates the front end portion C1 of the cathode C.

[0076] The top wall 212 is connected to the end of the side wall 211 on the target 31 side (electron emission direction side). The top wall 212 extends along a plane (YZ plane) orthogonal to the emission axis AX, covering the cathode C. The surface 212a of the top wall 212 on the target 31 side (electron emission direction side) is tapered in shape, moving closer to the target 31 side as it moves away from the emission axis AX. A circular opening 212b extending along the X-axis is provided at the center of the surface 212a. Therefore, the surface 212a forms a basin-shaped surface that slopes toward the opening 212b. The center of the opening 212b is located on the emission axis AX. The electron beam EB emitted from the electron emission surface EE of the front end portion C1 of the cathode C passes through the opening 212b. At least the electron emission surface EE in the front end portion C1 is disposed inside the opening 212b. In several embodiments, the front end portion C1 does not protrude to the target 31 side (electron emission direction side) compared to the opening 212b. Therefore, the electron emission surface EE does not protrude from the opening 212b.

[0077] The bottom wall 213 is connected to the end of the side wall 211 opposite to the end on the target 31 side (electron emission direction side). The bottom wall 213 extends along a plane (YZ plane) orthogonal to the emission axis AX. A pair of support pins C2 are provided at the center of the bottom wall 213, passing through a circular opening 213a that extends through the bottom wall 213 along the X-axis direction. The center of the opening 213a is located on the emission axis AX. The inner diameter of the opening 213a is larger than the inner diameter of the opening 212b. The bottom wall 213 has a flange 213b. Viewed from the direction along the emission axis AX (X-axis direction), the flange 213b is formed in an annular shape and extends outward from the side wall 211.

[0078] The first holding electrode 22 is a circular plate-shaped electrode connected to the first gate electrode 21. The material of the first holding electrode 22 is a metal with a high melting point (e.g., titanium, molybdenum, and alloys containing at least one of them). The first holding electrode 22 is disposed opposite to the side where the target 31 is located (electron emission direction side) relative to the first gate electrode 21. For example, the first holding electrode 22 is disposed in contact with the surface 213c of the bottom wall 213, which is opposite to the side of the target 31 (electron emission direction side). An opening 22a (central opening) extending in the X-axis direction is provided in the central portion of the first holding electrode 22. The center of the opening 22a is located on the emission axis AX. Furthermore, a circular through hole H is provided in the bottom wall 213 and the first holding electrode 22, which extends in the X-axis direction and connects the space S11 with the space S13 described later. In several embodiments, a plurality of through holes H (two in one example) are arranged at equal intervals along the circumference of the emission axis AX. Furthermore, two through holes H are arranged opposite each other across the emission axis AX. Two through holes H are also arranged opposite each other in the Y-axis direction. Each through hole H includes: a through hole 213f disposed in the bottom wall 213; and a through hole 22d disposed coaxially with the through hole 213f in the first holding electrode 22. In several embodiments, the through holes 213f and 22d, which coincide when viewed from the X-axis direction, form a through hole H connecting space S11 and space S13. When viewed from the X-axis direction, the outer edge of the first holding electrode 22 is located inside the outer edge of the flange portion 213b.

[0079] The rod portion 26 is a circular plate-shaped component to which the cathode C is fixed. The rod portion 26 has through holes through which a pair of support pins C2, serving as a power supply path, are inserted. The rod portion 26 contains an insulating material. The material of the rod portion 26 is, for example, alumina (Al2O3). The rod portion 26 is disposed within the opening 22a. The portion of the rod portion 26 protruding from the opening 22a is held by the second holding electrode 24, described later.

[0080] The second holding electrode 24 is disposed opposite to the first holding electrode 22 on the side opposite to the side where the target 31 is located (electron emission direction side). For example, the second holding electrode 24 is disposed in contact with the surface 22b of the first holding electrode 22 on the side opposite to the target 31 side (electron emission direction side). The material of the second holding electrode 24 is a high-melting-point metal (e.g., an alloy of copper and molybdenum, an alloy of copper and tungsten, etc.). The second holding electrode 24 has a sidewall 241 and a flange 242. The sidewall 241 is formed into a cylinder with the emission axis AX as the central axis. The flange 242 is annular and is connected to the end of the sidewall 241 on the target side (electron emission direction side), and extends to the outside of the sidewall 241 along a plane (YZ plane) orthogonal to the emission axis AX. The flange 242 is disposed in contact with the surface 22b of the first holding electrode 22. Viewed from the X-axis direction, the outer edge of the flange 242 is located inside the outer edge of the first holding electrode 22. In several embodiments, the outer edge of the flange 242 is located inside the edge on the emission axis AX side of the through hole H, such that the flange 242 does not block the through hole H. The inner surface 241a of the sidewall 241 is continuous with the opening 22a of the first holding electrode 22. In addition, the inner diameter of the sidewall 241 is the same as the inner diameter of the opening 22a. The rod 26 is received inside the opening 22a and the sidewall 241. In several embodiments, the rod 26 is inserted into the opening 22a of the first holding electrode 22. In addition, the outer surface of the portion of the rod 26 protruding from the opening 22a engages with the inner surface 241a of the sidewall 241 of the second holding electrode 24, and the surface 22b of the first holding electrode 22 engages with the flange 242. Therefore, the rod 26 can be selectively located and fixed to the electron gun 2.

[0081] like Figure 9 and Figure 12 As shown, the third holding electrode 25 surrounds at least a portion of the cathode C (e.g., a portion of a pair of support pins C2). The third holding electrode 25 has a sidewall 251 (the third sidewall) and a holding portion 252.

[0082] The sidewall 251 is formed as a cylinder with the emission axis AX as its central axis. An opening 251a (the third opening) is provided in the sidewall 251. In several embodiments, a plurality of openings 251a (two in one example) are provided in the sidewall 251. The two openings 251a are opposite each other in a direction orthogonal to the emission axis AX (the Z-axis direction in one example). The corners of each opening 251a are formed into a generally rectangular shape with a curved surface (R-shape). The length of the side of each opening 251a along the emission axis AX is approximately equal to the length of the sidewall 251 along the emission axis AX. The space S13 (the third space) surrounded by the sidewall 251 communicates with the space outside the sidewall 251 (space S14 described later) via the openings 251a.

[0083] The holding portion 252 is annular and connected to the end of the sidewall 251 on the target 31 side (electron emission direction side). The holding portion 252 holds the first holding electrode 22. Furthermore, the holding portion 252 has a portion 252a (first part) on the target 31 side (electron emission direction side) and a portion 252b (second part) on the opposite side to the target 31 side. The inner diameter of portion 252a is approximately the same as the outer diameter of the first holding electrode 22. The inner diameter of portion 252b is smaller than the inner diameter of portion 252a and larger than the outer diameter of the flange portion 242 of the second holding electrode 24, and is the size that does not block the through hole H. In several embodiments, the inner surface of portion 252b is located outside the edge of the through hole H on the opposite side to the emission axis AX. The side surface 22c of the first holding electrode 22 along the X-axis direction abuts against the inner surface of portion 252a. The outer edge of the surface 22b of the first holding electrode 22 abuts against the surface 252c of the target 31 side (electron emission direction side) of the portion 252b. In addition, the outer edge of the surface 22b of the first holding electrode 22 is placed on the surface 252c of the portion 252b.

[0084] like Figures 6-9 As shown, the second gate electrode 23 houses: a cathode C, a first gate electrode 21, a first holding electrode 22, a second holding electrode 24, a third holding electrode 25, and a rod portion 26. The second gate electrode 23 is formed in a cylindrical shape with the emission axis AX as its central axis. In several embodiments, the second gate electrode 23 has a sidewall 231 (second sidewall) formed in a cylindrical shape with the emission axis AX as its central axis. The end of the sidewall 231 on the target 31 side (electron emission direction side) has a curved surface shape (R-shape).

[0085] The sidewall 231 has a cap-like surrounding portion 232 that surrounds (accommodates) the flange portion 213b of the first gate electrode 21 and the holding portion 252 of the third holding electrode 25. The surrounding portion 232 includes the end of the sidewall 231 on the target 31 side (electron emission direction side). The surrounding portion 232 has a portion 232a (first portion) on the target 31 side (electron emission direction side) and a portion 232b (second portion) opposite to the target 31 side. The surrounding portion 232 is thicker than other portions of the sidewall 231 (e.g., the portion where the opening 231b is provided, described later). The thickness of portion 232a is greater than the thickness of portion 232b. In several embodiments, the portion of the sidewall 231 including the end on the target 31 side (electron emission direction side) (the surrounding portion 232) has a structure in which the thickness increases stepwise (stepwise) towards the target 31 side. The inner diameter of the sidewall 231 at part 232a is larger than the outer diameter of the sidewall 211 of the first gate electrode 21, but smaller than the outer diameter of the flange portion 213b of the first gate electrode 21. In addition, the inner diameter of the sidewall 231 of other parts where the opening portion 231b is provided is the same as the outer diameter of the holding portion 252 of the third holding electrode 25.

[0086] The flange portion 213b is fixed by portions 232a and 232b of the surrounding portion 232. For example, the flange portion 213b is fixed by abutting against the surface 232c of portion 232a, which is opposite to the target 31 side, through the surface 213d of the flange portion 213b on the target 31 side (electron emission direction side). In addition, the side surface 213e of the flange portion 213b along the X-axis direction is surrounded by the inner surface of portion 232b.

[0087] The holding portion 252 is surrounded by the portion 232b of the surrounding portion 232 and the outer portion of the sidewall 231 that has the opening 231b. For example, the target 31 side (electron emission direction side) surface 252d of the holding portion 252 abuts against the surface 232d of the portion 232b that is opposite to the target 31 side. In addition, the outer side surface 252e of the holding portion 252 along the X-axis direction is surrounded by the inner surface of the other portions of the sidewall 231.

[0088] The sidewalls 211 of the first gate electrode 21 and 231 (part 232a of the surrounding portion 232) of the second gate electrode 23, which are opposite to each other, are separated from each other by a space S12 (second space). In several embodiments, the space S12 is an annular gap formed between the sidewalls 211 and the portion 232a. In addition, at the end of the sidewall 231 on the target 31 side (i.e., the end of the portion 232a), an opening 231a (second opening) is provided in the X-axis direction to communicate with the space S12 and the external space of the electron gun 2 (e.g., the internal space S1 of the frame 6). The end of the opening 231a on the target 31 side (electron emission direction side) has a curved shape (R-shape).

[0089] Viewed from a direction orthogonal to the X-axis (along the YZ plane), the sidewall 231 is configured to cover and conceal the opening 211a of the first gate electrode 21. Figure 9 As shown, the end face 231c of the sidewall 231 on the target 31 side (electron emission direction side) is located near the edge of the opening 211a on the target 31 side. Therefore, when the electron gun 2 is viewed in a direction perpendicular to the emission axis AX (e.g., when viewed from the Y-axis or Z-axis direction), at least a portion of the top wall 212 (the end face of the target 31 side (electron emission direction side)) can be seen, but the opening 211a covered by the second gate electrode 23 cannot be seen.

[0090] like Figure 13 As shown, a space S14 (fourth space) is formed between the portion of the sidewall 231 opposite to the sidewall 251 of the third holding electrode 25 (i.e., the portion surrounding the sidewall 251) and the sidewall 251. The sidewalls 231 and 251 are separated from each other by a gap between them. Furthermore, an opening 231b (fourth opening) is provided in the portion of the sidewall 231 opposite to the sidewall 251 (the portion surrounding the sidewall 251). In several embodiments, a plurality of openings 231b (two in one example) are provided in the sidewall 231. The two openings 231b are opposite each other in a direction orthogonal to the emission axis AX (Y-axis direction in one example). Each opening 231b, like the opening 251a, has a curved edge (R-shaped) and is generally rectangular. The space S14 between sidewall 251 and sidewall 231 is connected to the external space of electron gun 2 (e.g., the internal space S1 of frame 6) via opening 231b.

[0091] like Figure 13 As shown, the opening 251a on the side wall 251 and the opening 231b on the side wall 231 are not directly opposite each other. In several embodiments, when viewed from the X-axis direction, the position of the opening 251a is offset by approximately 90 degrees relative to the position of the opening 231b. Therefore, when the electron gun 2 is viewed from the outside, the openings 231b and 251a are staggered from each other so that the opening 251a is not visible through the opening 231b.

[0092] In several embodiments, the space S11 within the first gate electrode 21 (the cathode receiving space that accommodates the front end C1 of the cathode C) communicates via an opening 211a provided in the sidewall 211 of the first gate electrode 21, and a space S12 between the sidewall 211 and the sidewall 231 (part 232a of the surrounding portion 232) of the second gate electrode 23. Furthermore, the space S12 communicates with the external space of the electron gun 2 (e.g., the internal space S1 of the frame 6) via the opening 231a provided in the second gate electrode 23. Thus, gas remaining in the cathode receiving space (space S11) is discharged into the space S12 via the opening 211a, and the gas discharged into the space S12 is discharged into the external space of the electron gun 2 (e.g., the internal space S1 of the frame 6) via the opening 231a. Therefore, the electron gun 2 can be used for efficient vacuum venting of the cathode receiving space (space S11). In addition, there are cases where each component of the electron gun 2 (e.g., the first gate electrode 21) generates gas, but the exhaust of such gas can also be carried out efficiently. In this way, the electron gun 2 is configured to efficiently exhaust the vacuum of the cathode housing space (space S11), thereby suppressing the consumption of the cathode C and the discharge between components (e.g., corona discharge between the support pin C2 and each electrode).

[0093] The opening 211a has an elongated shape that extends circumferentially around the ejection axis AX in order to allow vacuum exhaust within the space S11 through the opening 211a.

[0094] The sidewall 231 is configured to cover and conceal the opening 211a when viewed from a direction orthogonal to the emission axis AX (along the YZ plane). This conceals structures where the edge of the opening 211a has a large potential difference with the electron gun relative to the inner wall of the frame 6. As a result, the generation of discharge can be suppressed.

[0095] The third holding electrode 25 has a sidewall 251 that surrounds a support portion (a pair of support pins C2) supporting the front end C1 of the cathode C around the emission axis AX. An opening 251a is provided in the sidewall 251 to communicate with the space S13 surrounded by the sidewall 251 and the external space of the electron gun 2 (e.g., the internal space S1 of the frame 6). Thus, gas remaining in the cathode housing space (space S13) containing the pair of support pins C2 can be discharged to the external space of the electron gun 2 (e.g., the internal space S1 of the frame 6) via the opening 251a. Alternatively, gas may be generated from the components constituting the electron gun 2 (e.g., the third holding electrode 25), but such gas discharge can also be performed efficiently.

[0096] A through-hole H connecting space S11 and space S13 can be provided in electron gun 2. Based on the above configuration, vacuum exhaust within space S13 can be performed more effectively.

[0097] In several embodiments, a portion of the sidewall 231 surrounds the sidewall 251 around the emission axis AX. In this portion of the sidewall 231 surrounding the sidewall 251, an opening 231b is provided that communicates the space S14 between the sidewalls 231 and 251 with the external space of the electron gun 2 (e.g., the internal space S1 of the frame 6). The space S13 communicates with the external space of the electron gun 2 (e.g., the internal space S1 of the frame 6) via the space S14. Thus, in a configuration where the sidewall 231 of the second gate electrode 23 surrounds the sidewall 251 of the third holding electrode 25, gas remaining in the space S13 can also be discharged to the external space of the electron gun 2 (e.g., the internal space S1 of the frame 6) via the opening 251a, the space S14, and the opening 231b. Alternatively, there may be cases where gas is generated from the components constituting the electron gun 2 (e.g., the third holding electrode 25), but even in such cases, gas discharge can be performed efficiently.

[0098] The openings 251a and 231b are configured not to face each other. The openings 251a and 231b are arranged such that the opening 251a is not visible through the opening 231b, thereby concealing structures such as the edge of the opening 251a that have a large potential difference with the electron gun relative to the inner wall of the frame 6. This suppresses the generation of discharge.

[0099] Evaluation experiments using an X-ray generating apparatus 1 with an electron gun 2 in an embodiment confirmed that no discharge occurs at a tube voltage of 160 kV after adjustment. Furthermore, as a result of not generating discharge, compared to a structure without openings 211a, 231a, 251a, and 231b, it was confirmed that the consumption of cathode crystals constituting the cathode C can be significantly reduced.

[0100] It should be understood that all the methods, advantages, and features described in this specification are not necessarily achieved by any particular embodiment, or are not necessarily included in any particular embodiment. Various embodiments have been described in this specification, but it should be understood that other embodiments involving different materials and shapes may also be employed.

[0101] For example, if the emission axis of the electron beam EB from the electron gun 2 is well 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 positioned between the magnetic focusing lens 42 and the magnetic quadrupole lens 43, or between the magnetic quadrupole lens 43 and the target 31.

[0102] The shape of the electron passage path P (cylindrical tube 9) can have a single diameter throughout the entire circuit. Alternatively, the electron passage path P can be formed by a single cylindrical tube 9. In other examples, the cylindrical tube 9 may only be provided within the frame 6, and the electron passage path P within the frame 7 may be formed by a through hole provided in the wall 71 of the frame 7. Alternatively, the cylindrical tube 9 may not be provided separately, and the electron passage path P may be formed by the through hole of the cylindrical member 10 and the through holes provided in the frame 44 and the frame 7.

[0103] Figure 6 This represents a first variation of the cylindrical tube (cylindrical tube 9A). In several embodiments, the cylindrical tube 9A has cylindrical portions 91A to 93A replacing cylindrical portions 91 to 96 at the points where cylindrical portions 91A to 93A replace cylindrical portions 91 to 96. Figure 2 The cylindrical tube 9 shown is different. A cylindrical portion 91A extends from end 9a of the cylindrical tube 9 to the position of coil 42a surrounded by the electron gun 2. The cylindrical portion 91A has a conical shape. For example, the diameter of the cylindrical portion 91A gradually increases from diameter d1 to diameter d2 towards the target 31 side. A 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 electrode 42b. The cylindrical portion 92A has a fixed diameter (diameter d2). A cylindrical portion 93A extends from the end of the cylindrical portion 92A on the target 31 side to 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 diameter d2 to diameter d6 towards the target 31 side from this end of the cylindrical portion 92A. In the cylindrical tube 9A, the cylindrical portion 91A corresponds to the diameter-enlarging portion, and the cylindrical portion 93A corresponds to the diameter-reducing portion.

[0104] Figure 7 This represents a second variation of the cylindrical tube (cylindrical tube 9B). In several embodiments, the cylindrical tube 9B is located at points where cylindrical portions 91B and 92B replace cylindrical portions 91 to 96. Figure 2 The cylindrical tube 9 shown is different. A cylindrical portion 91B extends from end 9a of the cylindrical tube 9 to a position surrounded by the electrode plate 42b. The cylindrical portion 91B has a conical shape. For example, the diameter of the cylindrical portion 91B gradually increases from diameter d1 to diameter d2 towards the target 31 side. A cylindrical portion 92B extends from the end of the cylindrical portion 91B on the target 31 side to end 9b of the cylindrical tube 9. The cylindrical portion 92B also has a conical shape. In several embodiments, the diameter of the cylindrical portion 92B gradually decreases from diameter d2 to diameter d6 towards the target 31 side from this end of the cylindrical portion 91B. In the cylindrical tube 9B, the cylindrical portion 91B corresponds to the diameter-enlarging portion, and the cylindrical portion 92B corresponds to the diameter-reducing portion.

[0105] In several embodiments, the diameter-reducing and diameter-expanding portions of the cylindrical tube (electron passage path) may not be formed in a stepped (discontinuous) shape as in cylindrical tube 9, but rather in a conical shape as in cylindrical tubes 9A and 9B. Alternatively, as in cylindrical tube 9B, the cylindrical tube may consist only of the conical portion. Furthermore, the cylindrical tube may have both a portion that varies in diameter in a stepped manner and a portion that varies in diameter in a conical shape. For example, the diameter-expanding portion may be conical as in cylindrical tube 9A, while the diameter-reducing portion may be stepped as in cylindrical tube 9.

[0106] Alternatively, the target may not be a rotating anode. In several embodiments, the target may be configured not to rotate, and the electron beam EB may always be incident on the same position on the target. However, by making the target a rotating anode, the localized load on the target caused by the electron beam EB can be reduced. As a result, the amount of electron beam EB can be increased, and the amount of X-rays XR emitted from the target can be increased.

[0107] In several embodiments, the electron gun 2 may also be configured to emit an electron beam EB having a circular cross-sectional shape. In other examples, the electron gun 2 may also be configured to emit an electron beam having a cross-sectional shape other than a circle.

[0108] In several embodiments, the openings 211a, 231a, 251a, and 231b described above may not be provided in the electron gun 2. For example, openings 251a and 231b may be omitted. In this case, the exhaust efficiency of space S11 can be improved by openings 211a and 231a. Furthermore, the shape, number, and arrangement of one or more of the openings 211a, 231a, 251a, 231b, and the through hole H can be changed. Additionally, the through hole H can also connect space S12 and space S13. The location where the through hole H is formed can be a location that coincides with space S12 when viewed from the X-axis direction (i.e., a relatively...). Figure 9 The position shown is on the outer side and far from the exit axis AX.

[0109] [Structure 1]

[0110] The first electrode includes a first gate electrode 21, the second electrode includes a second gate electrode 23, and the third electrode includes a holding electrode 25.

[0111] [Structure 2]

[0112] The electron gun 2 further includes a first holding electrode 22 connected to the first gate electrode 21 and a second holding electrode 24 connected to the first holding electrode 22. The first holding electrode 22 is located between the first gate electrode 21 and the second holding electrode 24.

[0113] [Structure 3]

[0114] The first holding electrode 22 has a circular plate-shaped metal electrode.

[0115] [Structure 4]

[0116] The first holding electrode 22 has a plurality of circular through holes 22d arranged at equal intervals along the circumference of the emission axis AX.

[0117] [Structure 5]

[0118] Multiple circular through holes 22d connect at least one of the first space (space S11) and the second space (space S12) to the third space (space S13).

[0119] [Structure 6]

[0120] The second holding electrode 24 has a cylindrical sidewall 241 and an annular flange 242.

[0121] [Structure 7]

[0122] The outer edge of the annular flange 242 is located inside the edge of at least one circular through hole 22d.

[0123] [Structure 8]

[0124] The first holding electrode 22 is provided with a central opening (opening 22a) located on the emission axis AX. The electron gun 2 further includes a rod 26 that supports the cathode C and is inserted into the central opening (opening 22a).

[0125] [Structure 9]

[0126] The second holding electrode 24 has a cylindrical sidewall 241. The outer surface of the rod portion 26, which protrudes from the central opening (opening 22a), is engaged with the inner surface 241a of the cylindrical sidewall 241.

[0127] [Structure 10]

[0128] The second space (space S12) located between the first sidewall 211 and the second sidewall 231 forms an annular gap.

[0129] [Structure 11]

[0130] The front end C1 of the cathode C is located in the first space (space S11).

[0131] [Structure 12]

[0132] The front end C1 of the cathode C emits the electron beam EB toward the external space (the internal space S1 of the frame 6).

Claims

1. An electron beam generator, wherein, have: The cathode has a front end that emits the electron beam; A first electrode, which houses the front end portion of the cathode, has a first sidewall surrounding the front end portion about the emission axis of the electron beam; and The second electrode has a second sidewall that surrounds the first electrode when viewed along the emission axis, is separate from the first sidewall, and surrounds the first sidewall. A first opening is provided on the first sidewall, which connects a first space surrounded by the first sidewall and a second space between the first sidewall and the second sidewall. The second electrode has a second opening that opens in a direction along the emission axis, thereby communicating the second space with the external space of the electron beam generator. The second sidewall is configured to cover and conceal the first opening when viewed from a direction orthogonal to the emission axis.

2. The electron beam generator as claimed in claim 1, wherein, The first opening has an elongated hole shape that extends circumferentially around the emission axis.

3. The electron beam generator as claimed in claim 1, wherein, It also includes: a third electrode having a third sidewall that surrounds a support portion supporting the front end of the cathode around the emission axis. A third opening is provided on the third sidewall, which allows the third space surrounded by the third sidewall to communicate with the external space.

4. The electron beam generator as claimed in claim 3, wherein, It also includes a through hole that connects at least one of the first space and the second space to the third space.

5. The electron beam generator as claimed in claim 3, wherein, It also includes: a fourth opening, which is provided in the portion of the second sidewall surrounding the third sidewall, so that the fourth space between the second sidewall and the third sidewall communicates with the external space. The third space is connected to the external space via the fourth space.

6. The electron beam generator as claimed in claim 5, wherein, The third opening and the fourth opening are not opposite to each other.

7. The electron beam generator as claimed in claim 3, wherein, The first electrode includes a first gate electrode. The second electrode includes a second gate electrode. The third electrode includes a holding electrode.

8. The electron beam generator as claimed in claim 7, wherein, It also has: A first holding electrode, which is connected to the first gate electrode; and The second holding electrode is connected to the first holding electrode. The first holding electrode is located between the first gate electrode and the second holding electrode.

9. The electron beam generator as claimed in claim 8, wherein, The first holding electrode has a circular plate-shaped metal electrode.

10. The electron beam generator as claimed in claim 8, wherein, The first holding electrode has a plurality of circular through holes that are equally spaced along the circumference of the emission axis.

11. The electron beam generator of claim 10, wherein, The plurality of circular through holes connect at least one of the first space and the second space to the third space.

12. The electron beam generator of claim 10, wherein, The second holding electrode has a cylindrical sidewall and an annular flange.

13. The electron beam generator of claim 12, wherein, The outer edge of the annular flange is located inside the edge of at least one of the circular through holes.

14. The electron beam generator as claimed in claim 8, wherein, The first holding electrode is provided with a central opening located on the emission shaft. The electron beam generator also features: The rod portion, which supports the cathode, is inserted into the central opening.

15. The electron beam generator of claim 14, wherein, The second holding electrode has a cylindrical sidewall. The outer surface of the rod protruding from the central opening engages with the inner surface of the cylindrical sidewall.

16. The electron beam generator as claimed in claim 1, wherein, The second space located between the first sidewall and the second sidewall forms an annular gap.

17. The electron beam generator as claimed in claim 1, wherein, The front end of the cathode is located in the first space.

18. The electron beam generator as claimed in claim 1, wherein, The front end of the cathode emits the electron beam into the external space.

19. An X-ray generating device, wherein, It possesses: the electron beam generator as described in claim 1.

20. An electron beam generator, wherein, have: The cathode has a front end that emits the electron beam; The first electrode, which houses the front end of the cathode, has a first sidewall surrounding the front end about the emission axis of the electron beam; The second electrode has a second sidewall that surrounds the first electrode when viewed along the direction of the emission axis, is separate from the first sidewall, and surrounds the first sidewall. The third electrode has a third sidewall that surrounds the support portion supporting the front end of the cathode around the emission axis; and A fourth opening is provided in the portion of the second sidewall that surrounds the third sidewall, thereby communicating the fourth space between the second and third sidewalls with the external space of the electron beam generator. A first opening is provided on the first sidewall, which connects a first space surrounded by the first sidewall and a second space between the first sidewall and the second sidewall. The second electrode has a second opening that opens in a direction along the emission axis, thereby communicating the second space with the external space. A third opening is provided on the third sidewall, which connects the third space enclosed by the third sidewall with the external space. The third space is connected to the external space via the fourth space.

21. An electron beam generator, wherein, have: The cathode has a front end that emits the electron beam; The first electrode, which houses the front end of the cathode, has a first sidewall surrounding the front end about the emission axis of the electron beam; A second electrode having a second sidewall that surrounds the first electrode when viewed along the emission axis, is separate from and surrounds the first sidewall; and The third electrode has a third sidewall that surrounds a support portion supporting the front end of the cathode around the emission axis. A first opening is provided on the first sidewall, which connects a first space surrounded by the first sidewall and a second space between the first sidewall and the second sidewall. The second electrode has a second opening that opens in a direction along the emission axis, thereby communicating the second space with the external space of the electron beam generator. A third opening is provided on the third sidewall, which connects the third space enclosed by the third sidewall with the external space. The first electrode includes a first gate electrode. The second electrode includes a second gate electrode. The third electrode includes a holding electrode. It also includes: a first holding electrode, which is connected to the first gate electrode; and The second holding electrode is connected to the first holding electrode. The first holding electrode is located between the first gate electrode and the second holding electrode.

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