JP2000030641A - X-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To position a grid electrode in the axial direction (electrode juxtaposing direction) accurately and easily. SOLUTION: The interval between a grid electrode 72 and a focusing electrode 25 is set to the prescribed interval by a spacer 8 which is made cylindrical not to interrupt the electrons 80 proceeding toward the focusing electrode 25 from the grid electrode 72, is fixed to the grid electrode 72 at an end section 8b on one side, and is kept in contact with the focusing electrode 25 at an end section 8c on the other side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray tube for generating X-rays.

[0002]

2. Description of the Related Art An X-ray tube includes an electron gun including a cathode, a heater, a grid electrode, and the like, a focusing electrode, and an anode target in a high-vacuum sealed housing (tube). Heat is generated by a heater to emit electrons from the cathode, and the electrons are focused and incident on an anode target to which a high voltage is applied via a grid electrode and a focusing electrode to generate X-rays.

In assembling the X-ray tube, an electron gun is inserted into the housing so as to face a focusing electrode integrated with the housing, and the position of the electron gun (position in the electron traveling direction) is determined. The lid portion of the gun opposite to the cathode is fixed to the housing and the housing is sealed.

Here, in the X-ray tube, in order to obtain a predetermined X-ray, an electron beam from an electron gun is irradiated on an anode target by 10 mm.
It is necessary to reduce the diameter to about μm. In order to obtain the predetermined focal diameter, the distance between the focusing electrode and the grid electrode of the electron gun needs to be a predetermined distance with high precision.

[0005]

However, the above X
In the case of a wire tube, when the electron gun is inserted into the housing in opposition to the focusing electrode, the housing is covered by a lid portion of the electron gun, and the actual distance between the grid electrode and the focusing electrode is changed. Since it is impossible to measure and inspect the electron gun, it is very difficult to precisely adjust the distance between the grid electrode and the focusing electrode to a predetermined distance by adjusting the position of the electron gun. There was a problem such as spending.

Incidentally, if the grid electrode is shifted from the focusing electrode by, for example, 100 μm with respect to a predetermined distance, a predetermined focal diameter (about 10 μm) cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and can accurately and easily position the grid electrode in the axial direction (the direction in which the electrodes are arranged), thereby improving the quality and reducing the assembly cost. An object is to provide an X-ray tube capable of realizing reduction.

[0008]

According to the X-ray tube of the present invention, a cathode is heated in a vacuum-sealed housing to emit electrons, and the electrons are emitted to an anode target via a grid electrode and a focusing electrode. In the X-ray tube that generates X-rays by converging on one end, one end is fixed to the grid electrode, the other end contacts the focusing electrode, and electrons from the grid electrode to the focusing electrode can pass through And a cylindrical spacer.

According to such an X-ray tube according to the present invention,
The grid electrode and the focusing electrode are formed by a spacer that is formed in a tubular shape so as not to block electrons traveling from the grid electrode to the focusing electrode, and one end is fixed to the grid electrode and the other end is in contact with the focusing electrode. Is set to a predetermined interval. Therefore, the positioning of the grid electrode in the axial direction (the direction in which the electrodes are arranged) can be performed accurately and easily. Excess X-rays from the anode target to the cathode side via the focusing electrode are shielded from the cathode side by the cylindrical spacer and the grid electrode fixing the spacer. For this reason, leakage of X-rays from the housing is more reliably prevented.

Here, the other end of the spacer and the focusing electrode are preferably fitted together by a fitting portion.

When such a configuration is adopted, the positioning of the other end of the spacer in the direction orthogonal to the electrode juxtaposition direction can be performed accurately and easily by the fitting of the fitting portion. The edge and the grid electrode are supported by the focusing electrode, and the earthquake resistance is improved.

Preferably, one end of the spacer and the grid electrode are fitted by a fitting portion.

In the case of adopting such a configuration, when fixing one end of the spacer to the grid electrode,
By the fitting of the fitting portions, the positioning of the end portion with respect to the grid electrode is performed accurately and easily.

Further, it is preferable that the housing is cooled by a cooling medium.

When such a configuration is adopted, the heat of the grid electrode is transferred to the spacer fixed to the grid electrode,
The heat is actively dissipated to the cooling medium via the focusing electrode and the housing that the spacer abuts. For this reason, abnormal heat generation in the grid electrode is prevented.

The spacer preferably has a gas vent hole in the peripheral wall.

In the case of adopting such a configuration, the space on the anode target side and the space on the cathode side defined by the cylindrical spacer and the grid electrode for fixing the spacer are degassed. Since the communication is established by the holes, the inside of the housing can be easily evacuated.

Further, the spacer and the housing are conductors,
Preferably, the focusing electrode is electrically connected to the housing, and a predetermined potential is supplied to the spacer.

When such a configuration is adopted, a predetermined potential is supplied to the housing via the spacer and the focusing electrode, and the potentials of the spacer, the focusing electrode and the housing are always maintained at a predetermined level. For this reason, the electrons from the cathode are normally focused on the anode target, and it is not necessary to separately supply a potential to the housing.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an X-ray tube according to the present invention will be described below with reference to the accompanying drawings.
In each of the drawings, the same elements are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 is a sectional view showing a main part of the X-ray tube according to the first embodiment. As shown in FIG. 1, the X-ray tube 1
A microfocus X-ray tube including an electron gun unit 2 that generates and emits electrons 80 and an X-ray generation unit 3 that receives the electrons 80 from the electron gun unit 2 and generates X-rays 81. . Each of the electron gun unit 2 and the X-ray generation unit 3 is configured by a cylindrical container 21 or 31 as a housing for housing each component. These containers 21 and 31 are made of a conductor and are connected to be orthogonal to each other.
The inside of the container 21 and the inside of the container 31 are separated by a focusing electrode 25 formed at the boundary between the containers 21 and 31, and are communicated through an opening 25 a formed in the focusing electrode 25. Reference numeral 50 denotes an anode target in the container 31. Container 2
1, 31 are sealed, and the inside thereof is evacuated.

The electron gun 50 disposed in the container 21 generally includes a heater 76 as a heat source, a cathode 73 as a thermoelectron source which generates and emits electrons 80 when heated by the heater 76, and a cathode 73. And second grid electrodes 7 for accelerating and focusing electrons 80 emitted from
1, 72, the second grid electrode 72 and the focusing electrode 25.
And a spacer 8 interposed between the second grid electrode 72 and the focusing electrode 25 to set a predetermined interval between the second grid electrode 72 and the focusing electrode 25, and a predetermined distance between the first and second grid electrodes 71 and 72, the heater 76, and the cathode 73. A plurality of pins 5 for supplying the voltage from outside of the container, and a stem 4 through which the pins 5 are fixed and which functions as a lid of the container.

The stem 4, the heater 76 and the cathode 7
3. First and second grid electrodes 71 and 72 and spacer 8
Are arranged side by side in this order toward the focusing electrode 25 side, and their respective axes coincide with each other, and are located coaxially with the axis of the opening 25a of the focusing electrode 25 and the axis of the cylindrical container 21. Are arranged as follows.

More specifically, the cathode 7
Numeral 3 is provided at the tip of a cylindrical body 74 made of an insulator. Inside the cylindrical body 74, the heater 76 for heating the cathode 73 is provided. The first grid electrode 71 includes:
The first electrode is disposed closer to the focusing electrode 25 than the cathode 73.
The second grid electrode 72 is disposed closer to the focusing electrode 25 than the grid electrode 71. This second grid electrode 72
Is supported on the focusing electrode 25 side of the first grid electrode 71 via a plurality of ceramic rods (insulators) 9, and the cylindrical body 74 having the cathode 73 and the heater 76 is connected to the focusing electrode 25 of the first grid electrode 71. On the side opposite to the 25th side, an insulator 7
5 is supported.

The first and second grid electrodes 71 and 72 each have a disk shape, and have openings 71 a and 72 a at positions facing the respective cathodes 73, through which electrons 80 from the cathodes 73 pass. The second grid electrode 72
This is an electrode that pulls electrons 80 from the cathode 73 toward the target 32 in the container 31. The first grid electrode 71 is an electrode that pushes electrons 80 pulled toward the target 32 by the second grid electrode 72 back to the cathode 73 side. By adjusting the voltage supplied to the first grid electrode 71, the first grid electrode 71 The number of electrons 80 going to the 32 side is increased or decreased. Also, the first and second grid electrodes 71 and 72
As shown in FIG. 2, the apertures 71a and 72a form a micro electron lens group that focuses electrons 80 from the cathode 73 to the target 32.

Returning to FIG. 1, a spacer 8 which characterizes the present embodiment is interposed between the second grid electrode 72 and the focusing electrode 25. The spacer 8 has a cathode 73
Has a predetermined length in the axial direction, and has one end 8b fixed to the end face of the second grid electrode 72 and the other end 8c Are brought into contact with the focusing electrode 25. The spacer 8 having the predetermined length is formed by the second grid electrode 72 and the focusing electrode 2.
5, the second grid electrode 72
And the focusing electrode 25 are set at a predetermined interval. Here, the predetermined interval is an interval between the second grid electrode 72 and the focusing electrode 25 necessary to obtain a desired focal diameter.

The spacer 8 is made of, for example, a conductor such as stainless steel, and the second grid electrode 72 for fixing the spacer 8 is made of, for example, Mo (molybdenum) having good heat resistance. As described above, in the present embodiment, Mo, which is difficult to perform normal welding, is used as the second grid electrode 72. Therefore, the second grid electrode 72 and the spacer 8 are formed by resistance welding using a plurality of Ni (nickel) ribbons 7. And are connected. The connection by the Ni ribbon 7 is made between the end surface of the second grid electrode 72 and the inner peripheral surface of one end 8 b of the spacer 8.

The spacer 8 has, on its peripheral wall, a space on the target 32 side and a space on the cathode 73 side defined by the spacer 8 and the second grid electrode 72 for fixing the spacer 8 as boundaries. Are provided with a plurality of holes 8a for venting gas.

The above-mentioned first grid electrode 71 has a plurality of pins 5 implanted on the side opposite to the target 32 side. These pins 5 are fixed to the stem substrate 4a through a disk-shaped stem substrate 4a made of an insulator such as ceramics. That is, the first grid electrode 71 that supports the spacer 8, the second grid electrode 72, the cylindrical body 74, and the like is supported by the stem substrate 4a via the plurality of pins 5.

A plurality of other pins (not shown) are also fixed through the stem substrate 4a. A lead wire 72f of the second grid electrode 72, a lead wire (not shown) of the cathode 73 and the heater 76 are connected to each of the plurality of other pins. An annular stem ring 4b is provided around the outer periphery of the stem substrate 4a.
Are joined.

The electron gun 50 is configured as described above. The stem ring 4b of the electron gun 50 is fixed to an opening 22 formed at an end of the container 21 by, for example, brazing. This stem ring 4b is the container 2
By being fixed to the opening 22, the opening 22 is covered by the stem 4 composed of the stem substrate 4 a and the stem ring 4 b, and the containers 21 and 31 are sealed.

A predetermined negative voltage is supplied to the first grid electrode 71 from outside the container via the pin 5 described above. A predetermined voltage is supplied to the heater 76 and the cathode 73 from outside the container via other pins and lead wires. Further, a ground potential is supplied to the second grid electrode 72 from the outside of the container via another pin and a lead wire 72f. The ground potential supplied to the second grid electrode 72 is also supplied to the spacer 8, the focusing electrode 25, and the containers 31, 21 electrically connected to the second grid electrode 72.

As shown in FIG. 3, the aperture 25a of the focusing electrode 25 located at the boundary between the containers 21 and 31 converts the electron beam focused by the first and second grid electrodes 71 and 72 into an elliptical shape. The shape is rectangular.

As shown in FIG. 1, the target 32 is provided in a container 31 which communicates with the container 21 through the opening 25a of the focusing electrode 25. The target 32 receives the electrons 80 from the electron gun 50 and receives the X-rays 8.
1, which forms a metal rod, and is arranged so that its axial direction crosses the direction in which the electrons 80 enter. The front end surface 32a of the target 32 is a surface that receives the electrons 80 from the electron gun 50, and is disposed at a position in front of the entrance of the electrons 80. The surfaces are inclined so as to be orthogonal. In addition, the target 32 includes:
A positive high voltage is applied.

The container 31 is provided with an X-ray emission window 33. The X-ray emission window 33 is a window for emitting the X-rays 81 emitted from the target 32 to the outside of the container 31, and is made of, for example, a plate made of a Be material that is an X-ray transmission material. . The X-ray emission window 33 is arranged in front of the front end of the target 32, and is formed so that the center thereof is located on the extension of the central axis of the target 32.

Next, the procedure for assembling the X-ray tube 1 will be described. First, the worker holds the spacer 8, the stem ring 4
b, and then assembling the electron gun 50. Then, the spacer 8 having a predetermined length with high dimensional accuracy in the axial direction is used in advance.
The second grid electrode 72 is fixed by resistance welding using the ribbon 7, and then the stem ring 4 b is attached to the stem substrate 4.
a. Next, the target 32 is placed in the container 31, and the assembled electron gun 50 is inserted into the container 21 from the opening 22.

Until the electron gun 50 abuts, that is, the other end 8c of the spacer 8 is
Insert until it abuts. When the other end 8c of the spacer 8 abuts on the focusing electrode 25, the spacer 8 sets the interval between the second grid electrode 72 and the focusing electrode 25 to a predetermined interval to obtain a desired focal diameter. To the required interval.

After the positioning of the electron gun 50 in the axial direction is completed, the stem ring 4b is joined to the opening 22 of the container 21 to seal the containers 21 and 31.

As described above, in the present embodiment, the positioning of the second grid electrode 72 (electron gun 50) in the axial direction can be performed accurately and easily by the spacer 8.

Incidentally, the inside of the containers 21 and 31 of the assembled X-ray tube 1 is in a vacuum state as described above. The evacuation of the inside of the containers 21 and 31 is performed from the container 21 side or the container 31 side. At this time, the plurality of gas vent holes 8a of the spacer 8 described above.
Accordingly, the space on the target 32 side and the space on the cathode 73 side defined by the spacer 8 and the second grid electrode 72 as boundaries are communicated with each other, so that the evacuation can be easily performed.

Next, the operation of the X-ray tube 1 configured as described above will be described. First, the X-ray tube 1 is immersed in, for example, insulating oil as a cooling medium. Then, a negative voltage is applied to the first grid electrode 71, a ground potential is applied to the second grid electrode 72, and a positive high voltage is applied to the target 32. Are supplied, the heater 76 is heated. Then, electrons 80 are emitted from cathode 73. The electrons 80 are accelerated and focused by passing through the openings 71a and 72a of the first and second grid electrodes 71 and 72, and are further focused on the opening 25a of the focusing electrode 25.
(See FIG. 2).

Since the opening 25a of the focusing electrode 25 has a rectangular shape as shown in FIG.
The electron beam that has passed through 5a becomes an ellipse and is focused and incident on the front end surface 32a of the target 32. At this time, since the distal end surface 32a is inclined, the X-ray 81 emitted from the distal end surface 32a becomes a perfect circle. And this X-ray 81
Are emitted out of the X-ray tube 1 through the X-ray emission window 33.

At this time, as described above, the distance between the second grid electrode 72 and the focusing electrode 25 is set to a predetermined distance by the spacer 8, and the distance between the second grid electrode 72 (electron gun 50) and the axial direction is set. Is accurately determined, a predetermined focal diameter is obtained at the distal end surface 32a of the target 32, and thus a predetermined X-ray 81 can be obtained.

Excess X-rays from the front end surface 32a of the target 32 to the cathode 73 through the opening 25a of the focusing electrode 25 are supplied to the cylindrical spacer 8 and the second grid electrode 72 for fixing the spacer 8. As a result, the X-ray is shielded from the cathode 73 side, so that leakage of X-rays from the container 21 can be more reliably prevented.

Further, since the X-ray tube 1 is immersed in insulating oil, the heat of the second grid electrode 72 is dissipated by the spacer 8 fixed to the second grid electrode 72 and the focusing electrode 25 contacted by the spacer 8. The heat is positively dissipated to the insulating oil through the containers 21 and 31, thereby preventing abnormal heat generation in the second grid electrode 72.

When the spacer 8 is made of a non-conductive material, X
When the wire tube 1 is operated, the spacers 8 may be charged and the electrons 80 from the cathode 73 may not be normally focused on the front end surface 32a of the target 32. In the present embodiment, the spacers 8 are used as conductors. Since the ground potential is supplied to the spacer 8 via the second grid electrode 72, abnormal charging of the spacer 8 is prevented, and electrons 80 from the cathode 73 can be normally focused on the front end surface 32 a of the target 32.

Further, the ground potential is also supplied to the containers 21 and 31 via the second grid electrode 72, the spacer 8 and the focusing electrode 25. Therefore, the ground is supplied to the containers 21 and 31 using another ground potential supply means. There is no need to supply a potential, and the number of components can be reduced.

FIG. 4 is a sectional view showing a main part of an X-ray tube according to the second embodiment. The X-ray tube of the second embodiment is
The difference from the embodiment (see FIG. 1) is that the focusing electrode 25
The thickness of the outer peripheral portion of the cathode 73 is made thicker, and the inner peripheral surface 25c of the thicker portion 25b is a fitting surface to the outer peripheral surface of the other end 8c of the spacer 8.

The inner peripheral surface 25c of the thick portion 25b has its axis aligned with the components of the electron gun 50 and the opening 2 of the focusing electrode 25.
It is formed so as to coincide with the axis of 5a.

The other end 8 of the spacer 8
In a state where the outer peripheral surface c is fitted to the inner peripheral surface 25c of the thick portion 25b, the other end 8c is in contact with the end surface of the focusing electrode 25 as in the first embodiment. .

It is needless to say that the same effect as that of the first embodiment can be obtained with such a configuration. In addition, the other end 8 c of the spacer 8 is fitted to the focusing electrode 25. Because of the combined configuration, the positioning of the other end 8c in the direction (vertical direction in the drawing) orthogonal to the direction in which the electrodes are arranged can be accurately and easily performed.

Further, by the fitting, the other end 8 c of the spacer 8 and the second grid electrode 72 are connected to the focusing electrode 25.
, It is possible to improve the earthquake resistance.

FIG. 5 is a sectional view showing a main part of an X-ray tube according to the third embodiment. The X-ray tube of the third embodiment is
The difference from the embodiment (see FIG. 4) is that the Ni ribbon 7
Instead, the outer peripheral surface of the second grid electrode 72 and the outer peripheral surface of one end 8 b of the spacer 8 are connected by a plurality of Ni ribbons 10.

Even with this configuration, the same effect as in the second embodiment can be obtained.

FIG. 6 is a sectional view showing a main part of an X-ray tube according to the fourth embodiment. The X-ray tube of the fourth embodiment is a third embodiment.
The difference from the embodiment (see FIG. 5) is that a groove 8d is annularly formed on the outer peripheral side of one end 8b of the spacer 8 and the groove 8d is formed on the spacer 8 side of the second grid electrode 72. The point is that the protruding portion 72d to be fitted is provided in an annular shape.

When assembling the electron gun 50, the spacer 8
Groove 8d at one end 8b and second grid electrode 72
The spacer 8 and the second grid electrode 72 are connected by the Ni ribbon 10 in a state where the protrusion 72d on the spacer 8 side is fitted.

It is needless to say that the same effect as in the third embodiment can be obtained with this configuration, and in addition, the groove 8d of the end 8b on one side of the spacer 8 can be obtained.
And the convex portion 72d on the spacer 8 side of the second grid electrode 72 is fitted, so that the positioning of the end 8b on one side of the spacer 8 with respect to the second grid electrode 72 can be performed accurately and easily.

FIG. 7 is a sectional view showing a main part of an X-ray tube according to the fifth embodiment. The X-ray tube of the fifth embodiment is the third
The difference from the embodiment (see FIG. 5) is that a groove 8e is provided annularly on the inner peripheral side of one end 8b of the spacer 8 and the groove 8e is provided on the spacer 8 side of the second grid electrode 72. This is the point that the convex portion 72e that fits in is provided in an annular shape.

It goes without saying that even with this configuration, the same effect as in the fourth embodiment can be obtained.

As described above, the invention made by the inventor has been specifically described based on the embodiments. However, the present invention is not limited to the above embodiments, and can be variously modified without departing from the gist thereof. Needless to say,
For example, in the fourth embodiment (see FIG. 6) and the fifth embodiment (see FIG. 7), the outer peripheral surface of one end 8b of the spacer 8 and the outer peripheral surface of the second grid electrode 72 are formed by the ribbon 10. The first embodiment (FIG. 1)
Similarly to the second embodiment (see FIG. 4), the joining may be performed on the inner peripheral surface side of one end 8b of the spacer 8.

In the above embodiment, since the second grid electrode 72 is made of Mo and the spacer 8 is made of stainless steel, it is more preferable that the second grid electrode 72 be made of resistance welding using Ni ribbons 7 and 10. The fixing method is as follows: Ni ribbon 7,
It is not limited to the resistance welding using No. 10, but when the second grid electrode 72 is made of, for example, stainless steel other than Mo, ordinary welding or brazing is adopted.

In the above embodiment, the cooling medium is insulating oil. However, the present invention is not limited to this. For example, an insulating gas or an insulating refrigerant may be used.

In the above embodiment, the reflection type microfocus X-ray tube is exemplified as the X-ray tube.
The present invention is not limited to this, and can be applied to, for example, a transmission type microfocus X-ray tube.

Further, the focal diameter is not limited to the microfocus, and the present invention can be similarly applied to an X-ray tube having any focal diameter.

[0065]

The X-ray tube according to the present invention has a cylindrical shape so as not to block electrons traveling from the grid electrode to the focusing electrode, and has one end fixed to the grid electrode and the other end focused. Since the distance between the grid electrode and the focusing electrode is set to a predetermined distance by the spacer abutting on the electrode, the grid electrode can be accurately and easily positioned in the axial direction (the direction in which the electrodes are arranged). As a result, it is possible to improve quality and reduce assembly costs. In addition, since extra X-rays from the anode target toward the cathode via the focusing electrode are shielded from the cathode by the cylindrical spacer and the grid electrode that fixes the spacer, Leakage of X-rays from the housing can be more reliably prevented, and the reliability of the X-ray tube can be further improved.

In the X-ray tube according to the present invention, since the other end of the spacer and the focusing electrode are fitted to each other by the fitting portion, the X-ray tube extends in the direction in which the electrodes are arranged at the end. Positioning in the orthogonal direction can be performed accurately and easily, and further improvement in quality and further reduction in assembly cost can be realized. Also, since the other end of the spacer and the grid electrode are supported by the focusing electrode by the fitting of the fitting portion, the earthquake resistance can be improved and the reliability of the X-ray tube can be further improved. It is possible to improve.

In the X-ray tube according to the present invention, since one end of the spacer and the grid electrode are configured to be fitted by the fitting portion, the end is fixed to the grid electrode. In this case, the positioning of the end portion with respect to the grid electrode can be performed accurately and easily, so that it is possible to further improve the quality and further reduce the assembly cost.

In the X-ray tube according to the present invention, the heat of the grid electrode is actively radiated to the cooling medium via the spacer fixed to the grid electrode, the focusing electrode in contact with the spacer, and the housing. Therefore, abnormal heat generation at the grid electrode can be prevented, and normal operation of the X-ray tube can be ensured.

In the X-ray tube according to the present invention, a hole for venting gas is provided in the peripheral wall of the spacer, and the anode target side defined by the cylindrical spacer and the grid electrode for fixing the spacer is defined as a boundary. Since the space and the space on the cathode side are configured to communicate with each other through the gas vent hole, the inside of the housing can be easily evacuated and the assembly cost can be further reduced. Becomes

In the X-ray tube according to the present invention, the spacer and the housing are used as conductors, and a predetermined potential is supplied to the spacer, and this potential is supplied to the housing via the spacer and the focusing electrode. Since the configuration is such that the potential of the focusing electrode and the casing is always maintained at a predetermined level, electrons from the cathode can be normally focused on the anode target, and the normal operation of the X-ray tube can be further ensured. In addition, it is not necessary to separately supply a potential to the housing, so that cost can be further reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of an X-ray tube according to a first embodiment.

FIG. 2 is an explanatory diagram showing a state of an electron beam from a cathode to an anode target.

FIG. 3 is an explanatory diagram showing a state of an electron beam incident on an anode target via a focusing electrode and an X-ray emitted from the anode target.

FIG. 4 is a sectional view showing a main part of an X-ray tube according to a second embodiment.

FIG. 5 is a sectional view showing a main part of an X-ray tube according to a third embodiment.

FIG. 6 is a sectional view showing a main part of an X-ray tube according to a fourth embodiment.

FIG. 7 is a sectional view showing a main part of an X-ray tube according to a fifth embodiment.

[Explanation of symbols]

1 X-ray tube, 7, 10 ribbon, 8 spacer, 8a
Hole for venting, 8b ... One end of spacer, 8c
... the other end of the spacer (the fitting part at the other end of the spacer), 8d, 8e ... the fitting part of the spacer (the fitting part at the one end of the spacer), 21, 31 ... container (Housing),
25: Focusing electrode, 25a: Opening of focusing electrode, 25c: Fitting portion of focusing electrode, 32: Anode target, 32a: Tip surface of anode target, 50: Electron gun, 71, 72 ... Grid electrode, 71a, 72a ... Opening of grid electrode, 72
d, 72e: Grid electrode fitting portion, 72f: Lead wire, 73: Cathode, 76: Heater, 80: Electronics, 81
... X-rays.

Claims (6)

[Claims] 1. An X-ray tube that heats a cathode to emit electrons in a housing sealed in a vacuum and focuses the electrons on an anode target via a grid electrode and a focusing electrode to generate X-rays. In the above, one end is fixed to the grid electrode, the other end is in contact with the focusing electrode, and a cylindrical spacer is formed so that electrons from the grid electrode toward the focusing electrode can pass therethrough. An X-ray tube, comprising: 2. The X-ray tube according to claim 1, wherein the other end of the spacer and the focusing electrode are fitted by a fitting portion. 3. The X-ray tube according to claim 1, wherein one end of the spacer and the grid electrode are fitted together by a fitting portion. 4. The X according to claim 1, wherein the housing is cooled by a cooling medium.
Wire tube. 5. The X-ray tube according to claim 1, wherein the spacer has a hole for venting gas on a peripheral wall. 6. The spacer and the housing are conductors, the focusing electrode is electrically connected to the housing, and a predetermined potential is supplied to the spacer. The X-ray tube according to any one of claims 1 to 5.