JP2003132825A - X-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray tube which enables reduction of a distance between a focusing position of an electron beam which generates X-ray there and a X-ray output window. SOLUTION: The X-ray tube 1 generates X-ray by collision to a target T of an electron beam emitted from an electron generating unit 3 in a hermetic envelope 2 which keeps vacuum inside the X-ray tube, and emits the X-ray in a direction approximately perpendicular to a direction of the electron beam via the X-ray output window 7a. An electron gun container 6 which contains the electron generating unit 3 is installed in the hermetic envelope 2 of the X-ray tube 1. The electron gun container 6 is formed in such a way that B is larger than A, wherein A is a length of the electron gun container 6 in X direction which is the x-ray output direction and B is a length of the electron gun container 6 in z direction which is the direction perpendicular to X direction and y direction which is the electron beam direction.

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, and more particularly to a microfocus X-ray tube in which the X-ray focus can be set extremely finely.

[0002]

2. Description of the Related Art Conventionally, an X-ray inspection apparatus having an X-ray tube as an X-ray generation source has been widely applied to non-destructive inspection, non-contact inspection and the like. For this type of X-ray inspection device,
It is required to further improve the magnifying power together with the sharpness of the fluoroscopic image to be captured. In this case, X in the X-ray tube
If the distance between the focus position of the line (X-ray generation point) and the sample or the like to be inspected can be shortened, the enlargement ratio of the X-ray inspection apparatus can be easily improved. Therefore, X
Various techniques have been proposed in order to shorten the distance between the focal position of a line and an inspection target or the like.

As such a technique, for example, those disclosed in Japanese Patent No. 2713860 and Japanese Patent Laid-Open No. 11-224625 are known. Patent No. 27
In the X-ray tube described in Japanese Patent No. 13860, a hood electrode having an electron passage hole is mounted around the target. A projection is formed on the end of the hood electrode on the X-ray output window side. When such a hood electrode is used, the equipotential surface between the hood electrode and the focus grid electrode approaches the focus grid electrode side. For this reason,
The electron beam accelerated between both electrodes bends toward the X-ray output window. As a result, the distance (FOD: Focus Object Distance) between the X-ray focal position and the X-ray output window is shortened. Further, in the X-ray tube described in JP-A-11-224625, the electron passage port of the hood electrode is enlarged on the side opposite to the X-ray traveling direction. As a result, the electron beam accelerated between the focus grid electrode and the hood electrode is further bent toward the X-ray output window.

[0004]

However, even if the conventional X-ray tube constructed as described above is used, the FOD may not be sufficiently shortened. That is, there is a limit to the size of the protrusion provided on the end of the hood electrode on the X-ray output window side. Therefore, it is difficult to further shorten the FOD by such a method. Further, when the electron passage port of the hood electrode is enlarged in the direction opposite to the X-ray traveling direction, the electron focusing property on the target is deteriorated, the spread of the electron beam is increased, and the focus shape is not circular. There was something that happened.

Therefore, an object of the present invention is to provide an X-ray tube which can easily and surely shorten the distance between the X-ray focal position and the X-ray output window.

[0006]

An X-ray tube according to the present invention as set forth in claim 1 is provided in a vacuum envelope by causing electrons emitted from an electron generating unit to collide with a target in the vacuum envelope. In the X-ray tube that outputs X-rays in a direction substantially orthogonal to the traveling direction of electrons through the output window, the vacuum envelope has a housing portion that houses the electron generation unit, and the housing portion includes: When the length in the output direction of the X-ray is A and the length in the direction orthogonal to both the output direction of the X-ray and the traveling direction of the electron is B, it is formed so as to satisfy B> A. It is characterized by

This X-ray tube is used in an X-ray inspection device or the like.
It is suitable for use as a line generation source, and includes an electron generation unit including a cathode that generates electrons, a target that serves as an anode, and a vacuum envelope that houses these. This vacuum envelope has a housing portion for housing an electron generation unit. Further, the vacuum envelope is provided with an output window so as to be parallel to the traveling direction of the electrons emitted from the electron generating unit. The cathode that receives electrons from the electron generation unit is arranged in the vacuum envelope so as to be inclined with respect to the traveling direction of the electrons and the output window. As a result, in this X-ray tube, when the electrons emitted from the electron generation unit in the vacuum envelope collide with the target, the X-ray is emitted from the output window of the vacuum envelope in a direction substantially orthogonal to the traveling direction of the electrons. Is output.

In the X-ray inspection apparatus and the like provided with this type of X-ray tube, it has been conventionally required to further improve the enlargement ratio. In order to realize this, it is necessary to further shorten the distance (FOD) between the X-ray focal point position and the X-ray output window on the X-ray tube side. Therefore, we have
We have earnestly studied in order to further shorten the FOD. And, based on various research studies, in this X-ray tube,
When the length in the X-ray output direction of the housing portion that houses the electron generation unit is A, and the length in the direction orthogonal to both the X-ray output direction and the electron traveling direction is B, B> It was decided to form the accommodation portion so as to satisfy A.

As described above, in the X-ray tube in which the electron traveling direction and the X-ray output direction are orthogonal to each other, forming the accommodating portion so as to satisfy B> A means that the output window is at the lower side. That is, the height in the cross section of the housing portion is less than the width. This makes it possible to bring the electron generation point of the electron generation unit closer to the output window side while ensuring a sufficient volume of the housing portion. Then, if the electron generation point in the electron generation unit approaches the output window side,
The X-ray focal point position on the target inevitably approaches the X-ray output window. As a result, according to this X-ray tube, the distance (FOD) between the X-ray focal position and the X-ray output window can be easily and surely shortened.

In this case, it is preferable that the accommodating portion is provided in the vacuum envelope so as not to project in the X-ray output direction from the output window.

That is, if the accommodating portion is constructed so that its bottom side is flush with the output window so as not to project in the X-ray output direction from the output window, the entire X-ray tube is inspected. It is possible to prevent the accommodation portion from becoming an obstacle when approaching. As a result, in an X-ray inspection apparatus or the like that employs this X-ray tube, it becomes possible to easily improve the enlargement ratio.

Further, various shapes can be adopted as the sectional shape of the accommodating portion for accommodating the electron generating unit within the range where B> A is satisfied. That is, the cross section of the accommodation portion is preferably polygonal such as rectangular or pentagonal, and may be elliptical. Further, as a cross section of the accommodating portion, a shape obtained by cutting a part of an ellipse with a straight line or a gentle curve (including a shape obtained by cutting a part of a perfect circle with a straight line or the like) may be adopted.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The X according to the present invention will now be described with reference to the drawings.
A preferred embodiment of the wire tube will be described in detail.

FIG. 1 is a sectional view showing an X-ray tube according to the present invention. The X-ray tube 1 shown in the figure is suitable for use as an X-ray generation source of an X-ray inspection apparatus, for example, and includes a vacuum envelope 2, an electron generation unit (electron gun) 3, and a target T. . The electron generation unit 3 has a cathode C in which porous tungsten or the like is impregnated with BaO or the like. The target T is formed by stacking an X-ray generation film made of tungsten or the like on a carbon layer with a protective layer interposed therebetween.
The electron generating unit 3 and the target T are housed inside the vacuum envelope 2, and the electrons emitted from the electron generating unit 3 inside the vacuum envelope 2 are the target T.
When it collides with, X-ray is output. The vacuum envelope 2 is shown in FIG.
As shown in FIG. 3, it is mainly composed of the envelope body 4 and the valve 10.

The envelope body 4 is a target T serving as an anode.
Body 5 in which is housed, and electron generating unit 3 serving as a cathode
And an electron gun accommodating portion 6 for accommodating therein. The body 5 is formed of metal or the like into a tubular shape and has an internal space 5a. Further, a flange portion 5b fixed to a casing of an X-ray inspection apparatus (not shown) is provided on the outer periphery of the body portion 5. The output window 7 is provided at the bottom of the body 5 in FIG.
A lid plate 7 having a is fixed, and the lid plate 7 closes one end side of the internal space 5a. On the other hand, the electron gun housing portion 6 is formed in a tubular shape as shown in FIG. 2, and is connected (fixed) to the lower side of the body portion 5. Figure 1
As shown in FIG. 5, the axis of the body 5 and the axis of the electron gun housing 6 are substantially orthogonal to each other, and the inside of the electron gun housing 6 has an aperture 6a.
Through the inner space 5a of the body 5.

The electron generating unit 3 accommodated in the electron gun accommodating portion 6 will be described. As shown in FIGS. 1 and 3, the electron generating unit 3 includes a cathode C and a heater 3.
0, first grid electrode 31 and second grid electrode 32
Is included. The cathode C, the heater 30, the first grid electrode 31, and the second grid electrode 32 each have a plurality of (in this embodiment, eight) pins 33 extending in parallel.
It is attached to the stem substrate 34 via a to 33h. Specifically, the cathode C is attached to a pin 33a (see FIG. 2) fixed to the stem substrate 34, and power is externally supplied through the pin 33a. Similarly, the heater 30 has a pin 3 fixed to the stem substrate 34.
3b and 33c (see FIG. 2), and power is supplied from the outside via these pins 33b and 33c.

Further, the first grid electrode 31 has pins 33d, 33e, 33f, 33 fixed to the stem substrate 34.
It is attached to g and is supplied with electric power from the outside through these pins 33d to 33g. In addition, the second grid electrode 3
2 is attached to a pin 33h fixed to the stem substrate 34, and power is externally supplied through the pin 33h. In this way, the electron generating unit 3 in which the cathode C and the like are integrated with the stem substrate 34 is inserted into the electron gun housing portion 6 from the end opposite to the aperture 6a, and the stem substrate 34 is the electron gun housing portion. It is fixed to the end of 6.

On the other hand, the valve 10 which constitutes the vacuum envelope 2 together with the envelope body 4 is formed in a substantially cylindrical shape from an insulating material such as glass or ceramic. As shown in Figure 1,
A ring member 8 made of metal or the like is fused to one end side (the lower end side in FIG. 1) of the valve 10. Then, the ring member 8 is joined (welded) to the body portion 5 that constitutes the envelope body 4. In this way, the one end of the valve 10 is joined to the envelope body 4.

On the other hand, the other end of the valve 10 (see FIG.
As shown in FIG. 1, a cylindrical inner cylinder portion 10a extending inward is provided on the upper end side in FIG. That is, the other end (upper end) of the valve 10 is folded back inward over the entire circumference so that a hole is defined in the center. As a result, the other end of the valve 10 is connected to the inner cylindrical portion 10
It is opened to the outside through the inside of a. And valve 1
A metal tube 11 for supporting the target T in the body portion 5 is attached to the inner cylinder portion 10 a of 0.

As shown in FIG. 1, the metal tube 11 basically has an outer diameter smaller than the inner diameter of the inner cylindrical portion 10a of the valve 10. Further, the metal tube 11 has an overhanging portion 11a on the outer circumference on one end side (lower end side in FIG. 1). That is, one end portion of the metal pipe 11 is folded back to the outside over the entire circumference, and a cylindrical portion (outer cylinder portion) having substantially the same diameter as the inner cylinder portion 10 a of the valve 10 is provided on the outer circumference on the one end side of the metal pipe 11. ) Has been formed. Then, the other end side (the upper end side in FIG. 1) of the metal tube 11 can be inserted into the inner cylindrical portion 10 a of the valve 10.

When the other end of the metal tube 11 is inserted into the inner cylindrical portion 10a of the valve 10, the end surface of the overhanging portion 11a comes into contact with the end surface of the inner cylindrical portion 10a provided on the valve 10. When the inner cylindrical portion 10a and the overhanging portion 11a come into contact with each other,
The other end of the metal tube 11 is, as shown in FIG.
It projects outward from the valve 10 via a. Then, the end surface of the valve 10 and the end surface of the protruding portion 11a are fused to each other.

The other end side of the target support 12 which supports the target T at one end side is inserted through the metal tube 11 thus attached to the valve 10. The target support 12 is formed in a rod shape with a copper material or the like, and the electron is increased from one end side (the lower end side in FIG. 1) toward the body part 5 side (from the upper side to the lower side in FIG. 1) toward the body side. It has an inclined surface 12a that inclines away from the generation unit 3 (see FIG. 1). The target T is embedded in the end portion of the target support 12 so as to be flush with the inclined surface 12a.

The other end (upper end in FIG. 1) of the target support 12 is welded to the end of the metal tube 11 protruding from the valve 10. As a result, the target support 12 extends substantially parallel to the axial center of the bulb 10 and the body 5, while being substantially orthogonal to the traveling direction y of the electrons from the electron generation unit 3. Therefore, the vacuum envelope 2
When electrons emitted from the electron generation unit (electron gun) 3 collide with the target T inside, the X-ray is output from the surface of the target T in a direction substantially orthogonal to the traveling direction of the electrons. The X-rays are emitted to the outside through the output window 7a of the cover plate 7 that covers the open end of the body 5 (the end opposite to the valve 10 side). In addition, inside the valve 10, the inner cylindrical portion 10
The cover electrode 14 is attached so as to cover the fusion-bonded portion between the a and the protruding portion 11a of the metal tube 11.

Now, the X-ray tube 1 constructed as described above
In the X-ray inspection apparatus and the like equipped with, it has been conventionally required to further improve the enlargement ratio. In order to realize this, it is necessary to further shorten the distance (FOD) between the X-ray focal point position and the output window 7a on the X-ray tube side. For this reason, the present inventors have made extensive studies in order to further shorten the FOD. Then, based on various studies and studies, in this X-ray tube 1, as shown in FIG. 2, the X-ray output direction x of the electron gun housing portion 6 housing the electron generation unit 3 is output.
The length in (see FIG. 1) is A, and the X-ray output direction x
And B is the length in the direction z (see FIG. 2) orthogonal to both the electron traveling direction y (see FIG. 1) and B>
The electron gun housing portion 6 is formed so as to satisfy A.

That is, as shown in FIG. 2, the electron gun housing portion 6 of the X-ray tube 1 has a substantially rectangular cross section in which the height A in the cross section is smaller than the width B when the output window 7a is on the lower side. In accordance with this, the stem substrate 34 also has a rectangular cross section. As a result, the electron generation point in the electron generation unit 3 can be brought closer to the output window 7a side in the x direction shown in FIG. 1 while ensuring the necessary and sufficient volume of the electron gun housing portion 6. In this way, if the electron generation point in the electron generation unit 3 approaches the output window 7a side, the X-ray focal point position on the target T inevitably approaches the output window 7a. Therefore, according to the X-ray tube 1, the distance (FOD) between the X-ray focal position and the output window 7a can be easily and surely shortened.

Further, as shown in FIG. 1, in the X-ray tube 1,
The electron gun housing portion 6 is joined to the body portion 5 so that its bottom portion 6b is flush with the lid plate 7 having the output window 7a. That is, the electron gun housing portion 6 of the X-ray tube 1 does not project in the X-ray output direction x from the output window 7a. In this way, if the bottom portion 6b of the electron gun housing portion 6 is configured to be at least flush with the output window 7a so that it does not project in the X-ray output direction x from the output window 7a, X-rays can be obtained. It is possible to prevent the electron gun housing portion 6 from becoming an obstacle when the entire tube 1 is brought close to the inspection target or the like. As a result, in an X-ray inspection apparatus or the like that employs this X-ray tube 1, it is possible to easily improve the enlargement ratio.

As described above, the stem substrate 34 fixed to the electron gun housing portion 6 has a plurality of pins 33a-3.
3h is attached, and these pins 3 are attached to the cathode C and the like.
Electric power is supplied via 3a or the like. Therefore, from the standpoint of withstand voltage, it is necessary to maintain a certain distance between the pins 33a to 33h, and the stem substrate 34 requires a certain area. From this point of view, it is preferable to set the width B in the cross section of the electron gun accommodating portion 6 to be relatively large. As a result, a sufficient volume of the electron gun housing portion 6 can be secured, and a sufficient space can be maintained between the pins 33a to 33h on the stem substrate 34.

4 to 7 show another embodiment of the X-ray tube according to the present invention. As shown in these drawings, as the cross-sectional shape of the electron gun housing portion 6 housing the electron generation unit 3, various shapes can be adopted within a range that satisfies B> A.

For example, the X-ray tube 1A shown in FIG. 4 is provided with an electron gun housing section 6A having a substantially pentagonal cross section. In the X-ray tube 1A shown in the figure, the number of pins for integrating the cathode, the heater, the first grid electrode, and the second grid electrode (all not shown) forming the electron generating unit 3 into the stem substrate 34 is It is reduced compared to the X-ray tube 1 shown in FIGS. In this case, the cathode and the like are attached to the stem substrate 34A having a pentagonal cross section through the seven pins 35a to 35g.

To exemplify the correspondence between the cathode and the like in the X-ray tube 1A and the pin, the cathode is attached to the pin 35a fixed to the upper left end of the stem substrate 34 in the figure, and the heater is located below the center of the stem substrate 34. It is attached to the two fixed pins 35b and 35c. The first grid electrode is attached to the three pins 35d, 35e, 35f fixed to the center upper side and the left and right lower sides of the stem substrate 34. The second grid electrode is the stem substrate 34.
Is attached to a pin 35g fixed to the upper right side of the.

Even if such a construction is adopted, the distance (FOD) between the X-ray focal point position and the output window can be easily and surely shortened while securing the volume of the electron gun housing portion 6A as necessary and sufficient. You can Further, if the number of pins and the mounting positions are appropriately set, various polygons including a pentagon (for example, a triangle) can be adopted as the cross section of the electron gun housing portion.

Further, the X-ray tube 1B shown in FIG. 5 is provided with an electron gun housing portion 6B having a substantially elliptical cross section. In the X-ray tube 1B shown in the figure, the number of pins for integrating the cathode, the heater, the first grid electrode, and the second grid electrode (all not shown) forming the electron generating unit 3 into the stem substrate 34 is It is further reduced compared to the X-ray tube 1 shown in FIGS. 1 to 3 and the X-ray tube 1A shown in FIG. In this case, the cathode and the like are attached to the stem substrate 34B having an elliptical cross section through the six pins 36a to 36f.

As an example of the correspondence between the cathode and the like in the X-ray tube 1B and the pin, the cathode is attached to the pin 36a fixed to the upper left end of the stem substrate 34 in the figure, and the heater is fixed to the upper and lower center of the stem substrate 34. The two pins 36b and 36c are attached. The first grid electrode is attached to the two pins 36d and 36e fixed to the lower left and right sides of the stem substrate 34. Then, the second grid electrode is attached to the pin 36f fixed to the upper right side of the stem substrate 34. Even if such a configuration is adopted, while the volume of the electron gun housing portion 6B is ensured to be necessary and sufficient,
The distance (FOD) between the X-ray focal point position and the output window can be easily and surely shortened.

Further, the X-ray tube 1C shown in FIG. 6 is provided with an electron gun housing portion 6C having a cross section of a part of an ellipse cut by a straight line. Moreover, the X-ray tube 1 shown in FIG.
D is provided with an electron gun housing portion 6D having a shape obtained by cutting a part of a circle with a straight line, that is, having an approximately semicircular cross section. Even if these configurations are adopted, the distance (FOD) between the X-ray focal point position and the output window can be easily and surely shortened while the necessary and sufficient volumes of the electron gun housing portions 6C and 6D are secured. . In these cases as well, it goes without saying that the shapes of the stem substrates 34C and 34D are matched with the electron gun housing portions 6C and 6D. Further, as the correspondence relationship between the cathode and the like and the pins in the X-ray tubes 1C and 1D, the same one as illustrated in FIG. 5 can be adopted. Further, although not shown, as a cross section of the electron gun accommodating portion, a shape in which a part of an ellipse (a perfect circle) is cut with a gentle curve (a curve extending in the X-ray traveling direction side) may be adopted.

[0035]

As described above, in the X-ray tube according to the present invention, the electrons emitted from the electron generating unit are collided with the target in the vacuum envelope, and the output window provided in the vacuum envelope is opened. Through the X direction in a direction substantially orthogonal to the electron traveling direction.
A line is output, and the housing portion of the electron generation unit sets the length in the output direction of X-rays to A, and the length in the direction orthogonal to both the output direction of X-rays and the traveling direction of electrons. When B is set, B> A is satisfied. Therefore, in this X-ray tube, the distance between the X-ray focal position and the X-ray output window can be easily and surely shortened.

[Brief description of drawings]

FIG. 1 is a sectional view showing an X-ray tube according to the present invention.

FIG. 2 is a side view showing an X-ray tube according to the present invention.

FIG. 3 is a cross-sectional view for explaining the configuration inside the electron gun housing of the X-ray tube shown in FIGS. 1 and 2.

FIG. 4 is a side view showing a second embodiment of the X-ray tube according to the present invention.

FIG. 5 is a side view showing a third embodiment of the X-ray tube according to the present invention.

FIG. 6 is a side view showing a fourth embodiment of the X-ray tube according to the present invention.

FIG. 7 is a side view showing a fifth embodiment of the X-ray tube according to the present invention.

[Explanation of symbols]

1,1A. 1B. 1C. 1D ... X-ray tube, 2 ... Vacuum envelope, 3 ... Electron generation unit, 4 ... Envelope body, 5 ... Body part, 5a ... Internal space, 6, 6A, 6B, 6C, 6D ... Electron gun accommodating part , 6a ... Aperture, 6b ... Bottom part, 7 ... Lid plate, 7a ... Output window, 10 ... Valve, 12 ... Target support, 14 ... Cover electrode, 30 ... Heater, 31 ... First grid electrode, 32 ... Second grid Electrodes, 33a-33
h, 35a to 35g, 36a to 36f ... Pins, 34, 3
4A, 34B, 34C, 34D ... Stem substrate, C ... Cathode, T ... Target.

Claims (5)

[Claims] 1. An electron emitted from an electron generation unit in a vacuum envelope is made to collide with a target, and a direction substantially orthogonal to a traveling direction of the electron is passed through an output window provided in the vacuum envelope. In an X-ray tube that outputs X-rays, the vacuum envelope has a housing portion that houses the electron generating unit, and the housing portion has a length A in the X-ray output direction, and the X-ray The X-ray tube is formed so as to satisfy B> A, where B is the length in the direction orthogonal to both the output direction and the electron traveling direction. 2. The storage portion is provided with the X portion rather than the output window.
The X-ray tube according to claim 1, wherein the vacuum envelope is provided so as not to project in the output direction of the wire. 3. The X-ray tube according to claim 1, wherein the accommodation section has a polygonal cross section. 4. The X-ray tube according to claim 1, wherein the accommodation section has an elliptical cross section. 5. The X-ray tube according to claim 1, wherein a cross section of the accommodation portion has a shape obtained by cutting a part of an ellipse.