JP2002298772A - Transmissive radiation type x-ray tube and producing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmissive radiation type X-ray tube and a producing method thereof capable of increasing electron beam resistance and thereby increasing an amount of generated X-ray. SOLUTION: This transmissive radiation type X-ray tube is equipped with an X-ray transmissive window plate 37 airtightly jointed to a part of a vacuum container 33, an anode target thin film 39 directly or indirectly provided on a surface of the X-ray transmissive window plate 37 at vacuum side, and a cathode structure 35 for generating an electron beam irradiating the anode target thin film 39. At least a part of the anode target thin film 39 is a recessed surface 42 with respect to the cathode structure 35.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission radiation type X-ray tube and a method of manufacturing the same.

[0002]

2. Description of the Related Art An X-ray tube is an electron tube that collides an electron beam with an anode target placed in a vacuum vessel to generate X-rays from the anode target. It is used in analyzers and the like. Various types of X-ray tubes have been put into practical use according to applications. One of them is a microfocus transmitted-radiation X-ray tube having a small X-ray focus. 2. Description of the Related Art A microfocus transmitted-radiation X-ray tube is used in an X-ray magnifying fluoroscopic apparatus for magnifying and observing a semiconductor integrated circuit board or another object.

Here, an X-ray magnified fluoroscopy apparatus will be described with reference to FIG. X-ray shielded device case 11
The X-ray tube 12 is arranged inside the. X of X-ray tube 12
An object 13 such as a semiconductor integrated circuit board is disposed at a position away from the line generation focal position S by a distance La, and at a position further away from the object 13 by a distance Lb,
An X-ray area sensor 14, for example, a sensor surface of an X-ray image tube or a solid-state X-ray sensor is arranged.

[0004] The X-ray tube 12 is connected to a power supply 15 built in the apparatus case 11, and an operating voltage is supplied from the power supply 15 to the X-ray tube 12 under external control. The X-ray image signal output from the X-ray image signal output unit 16 of the X-ray area sensor 14 is transmitted to a monitor 17 incorporating an image processing device.
The X-ray magnified fluoroscopic image of the object 13 is displayed on the image display unit 18. The enlargement ratio M of the X-ray imaging of the object 13 is generally represented by M = (La + Lb) / La.

In this case, La << Lb is set, and as the distance La becomes smaller, the enlargement ratio M becomes larger. Further, the smaller the size of the focal point S of the X-ray tube, which is the X-ray source, the higher the resolution, and a clear X-ray magnified fluoroscopic image can be obtained.

Therefore, in the case of an X-ray magnifying fluoroscopy apparatus, it is desirable to arrange the focal point S of the X-ray tube, that is, the X-ray generation target portion as close to the object 13 as possible, and to reduce the distance La. For such a configuration, a microfocus transmission / radiation X-ray tube in which the X-ray generation target unit is provided at the forefront of the X-ray tube is suitable.

As shown in FIG. 10, an X-ray tube 12 of this type has a flat X-ray transmission window plate for transmitting X-rays at the tip of a metal cylindrical portion located on one side of a vacuum vessel 21. 22 is provided in a vacuum-tight manner. The X-ray transmission window plate 22 is usually
It is made of a material having a high X-ray transmittance such as beryllium. An anode target thin film 23 made of tungsten or the like is directly or indirectly attached to the vacuum-side surface of the X-ray transmission window plate 22 as shown in an enlarged manner in a main part. A cathode structure 24 for generating an electron beam and an electron gun 25 including a plurality of grid electrodes for an electron lens are arranged in a glass portion located on the other side in the vacuum vessel 21.

In the above-described configuration, the electron beam e generated from the cathode structure 24 forms a point focus S at the position of the anode target thin film 23 to generate X-rays. X-rays generated by the anode target thin film 23 are radiated to the outside through the transmission window plate 22 as they are, and used for X-ray imaging. in this case,
The emitted X-rays are indicated by the symbol X.

Such an apparatus or X-ray tube is disclosed, for example, in Japanese Patent Application No. 2000-229774, US Pat.
No. 771, Japanese Patent No. 2713860, Japanese Patent No. 2634369, Japanese Patent Publication No. 7-50594, Japanese Patent Application Laid-Open No. Hei 9-171788, Japanese Utility Model Publication No. 52-56778, and Japanese Utility Model Publication No. Sho 54-163885. It has been disclosed.

[0010]

In a conventional transmission-radiation X-ray tube, an anode target formed of a thin film of tungsten or the like is directly or indirectly mounted on a vacuum-side flat surface of an X-ray transmission window plate made of beryllium or the like. Is formed.

In this case, when the temperature of the anode target thin film rises due to the collision of the electron beam, the anode target thin film expands and generates thermal stress in the plane direction. This thermal stress causes the anode target thin film to separate from the X-ray transmission window plate, or causes cracks in the anode target thin film. When such damage occurs, the amount of X-rays emitted from the anode target thin film decreases, which hinders high performance and shortens the life.

The electron beam bombarding the anode target thin film formed of tungsten or the like is about 50% of the electron beam.
Is reflected with little loss of energy. The reflected electrons are accelerated again by the action of the accelerating electric field and collide with the surface of the anode target thin film which is far from the focal point. The recolliding backscattered electrons heat the anode target. Further, X-rays that are not used, so-called out-of-focus X-rays, are emitted, and the clarity of the X-ray image is impaired.

As described above, the reflected electrons only heat the anode target and do not contribute to the generation of useful X-rays.
Increasing the electron beam intensity to increase the X-ray dose is an obstacle to high performance.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks and to provide a transmission radiation type X-ray tube capable of increasing the electron beam intensity and increasing the amount of generated X-ray, and a method of manufacturing the same.

[0015]

According to the present invention, there is provided an X-ray transmission window plate hermetically bonded to a part of a vacuum vessel, and provided directly or indirectly on a vacuum-side surface of the X-ray transmission window plate. A transmission thin-film X-ray tube comprising a target thin film for generating X-rays and a cathode assembly for generating an electron beam for irradiating the target thin film, wherein at least a part of the target thin film is concave with respect to the cathode assembly. It is characterized by becoming.

[0016] Further, X air-tightly joined to a part of the vacuum vessel is used.
A X-ray transmitting window plate, a target thin film which directly or indirectly generates X-rays provided on the vacuum side of the X-ray transmitting window plate, and a cathode assembly which generates an electron beam for irradiating the target thin film. A method of manufacturing a transmission-radiation X-ray tube comprising: a first step of forming a concave surface on at least a part of a surface on the vacuum side of the X-ray transmission window plate; and forming the X-ray transmission panel having the concave surface. A second step of directly or indirectly forming the target thin film on the vacuum-side surface of the window plate.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. The microfocus transmission / radiation X-ray tube 30 includes a vacuum container 33 in which a glass container portion 31 and a metal cylindrical container portion 32 having a closed end are vacuum-tightly joined. The electron gun 3 is provided inside the vacuum vessel 33.
4 are arranged. The electron gun 34 includes a cathode structure 35 for generating an electron beam and a plurality of grid electrodes for an electron lens.

An X-ray emission window holding ring 36 is provided at the distal end of the metal cylindrical container portion 32 of the vacuum container 33. The X-ray emission window holding ring 36 has a high X-ray transmittance, for example, a diamond X-ray. The transmission window 37 is joined in a vacuum-tight manner. The diamond forming the X-ray transmission window 37 is, for example, metallized in a peripheral portion 38, and the ring 3 for holding the X-ray emission window is welded using the metallized portion.
6 is joined.

The X-ray emission window holding ring 36 is made of iron (F
e) or an iron alloy such as Kovar (trade name) or stainless steel, or a mechanically high-strength material such as copper (Cu) or a copper alloy. The tapered outer peripheral thin portion 36a is vacuum-hermetically joined to the distal end opening 32a of the metal cylindrical container portion 32 by heli-arc welding or the like.

A recess 41 is provided on the inner surface of the X-ray transmission window plate 37, that is, a part of the surface on the vacuum side, and an anode target made of tungsten (W) is provided on the X-ray transmission window plate 37 provided with the recess 41. A thin film 39 is formed, laminated and attached. In this case, in the portion of the concave portion 41 of the X-ray transmission window plate 37, the X-ray transmission window plate 37 is formed on the concave surface 42 toward the cathode structure 35. For example, the X-ray focus S
Is formed.

As shown in the enlarged view of FIG. 2, the X-ray transmitting window plate 37 has, for example, a concave portion 41 which is recessed from the peripheral portion, and is provided on the X-ray transmitting window plate 37 provided with the concave portion 41. The anode target thin film 39 adheres to the substrate.

When the above-mentioned X-ray tube enters the operating state, it is generated from the cathode assembly 35 and generated by the electron gun 34 as described in the prior art.
The electron beam e having passed through focuses on the concave surface of the anode target thin film 39. Then, the X-ray generated at the focal point S
The light is radiated to the outside through the X-ray transmission window 37 as shown by the symbol X and used for X-ray photography or the like.

According to the above configuration, the anode target thin film 39 in the region where the focal point S of the electron beam e is formed is provided, for example, in the concave portion 41 of the X-ray transmission window plate 37.
It is concave with respect to the cathode structure 35. In this case, the temperature rise due to the collision of the electron beam e causes the anode target thin film 3
9 expands and generates a thermal stress in the plane direction of the anode target thin film 39, the thermal stress is generated by the anode target thin film 39.
Acts on the X-ray transmission window plate 37 to prevent peeling or cracking. Therefore, the generated X-ray dose can be increased by further increasing the electron beam intensity.

For example, the anode target thin film 39 is adhered to the X-ray transmission window plate 37 as a whole, and when thermally expanded by collision of an electron beam, a thermal stress is generated in the plane direction of the anode target thin film 39. At this time, since the surrounding portion is attached to the X-ray transmission window plate 37, for example, the X-ray transmission window plate 3
In the case where 7 is a convex surface, the shape is pushed from the peripheral portion, the thermal expansion portion rises, and peeling occurs, or a crack occurs. Even when the X-ray transmission window plate is flat, the surface usually has irregularities, and peeling or cracking occurs at the convex surface. on the other hand,
When the X-ray transmission window plate has a concave surface, the thermal stress in the concave portion acts so as to press the anode target thin film against the X-ray transmission window plate, so that separation does not occur. In addition, the thermal stress in the concave portion becomes a compressive stress, and the occurrence of cracks is also prevented.

In the above embodiment, the entire focal point S of the electron beam e is formed in the concave surface of the anode target thin film 39. However, even if a part of the focal point S of the electron beam e is outside the concave surface of the anode target thin film 39, when the main part of the thermal expansion portion is within the concave surface, the occurrence of peeling or cracking is suppressed.

Here, a film forming process for forming the anode target thin film 39 on the X-ray transmission window plate 37 will be described with reference to FIG. First, as shown in FIG. 3A, metallization of an X-ray transmission window plate 37 in which a recess 41 is formed in advance in a stepped portion 36b of an opening of a window holding ring 36 processed into a predetermined shape. A portion, for example, its peripheral portion 38 is joined.

Next, the window holding ring 36 to which the X-ray transmission window plate 37 is joined is disposed in the film forming apparatus, and the X-ray transmission window 37 is formed by a CVD method or the like as shown in FIG. A tungsten thin film 39 is formed and adhered on the inner surface.

Next, X on which the tungsten thin film 39 is formed
As shown in FIG. 1, a window holding ring 36 having a line transmitting window plate 37 is fitted into the distal end opening 32a of the metal cylindrical container portion, and the thin-walled cylindrical end portions which match both are joined in a vacuum-tight manner by heli-arc welding. To make a vacuum container. Thereafter, an electron gun or the like is incorporated in the vacuum vessel, and the X-ray tube is completed through an exhaust process and the like.

In the above-described method, the concave portion 41 is formed in a part of the X-ray transmission window plate 37, and thereafter, is joined to the window holding ring 36. However, the concave portion 41 may be formed in a part of the X-ray transmission window plate 37 after being joined to the X-ray transmission window plate holding ring 36.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In this embodiment, the anode target thin film 39 made of tungsten is formed so as to extend from the inner surface of the X-ray transmission window plate 37 to a point on the inner tapered surface of the transmission window holding ring 36. In the figure, the extension of the anode target thin film 39 is indicated by reference numeral 39a.

According to this embodiment, when forming the anode target thin film 39, there is an advantage that the masking for defining the film formation region may be relatively rough.

In the embodiment shown in FIGS. 1 to 4, pure tungsten is used as the material of the anode target thin film. However, not limited to this, for example, rhenium (Re)
, A molybdenum-tungsten alloy containing a small amount of molybdenum (Mo), or a tungsten-based alloy containing a small amount of another element can also be used.

The X-ray transmission window plate is formed of diamond. In this case, since the thermal conductivity of diamond is higher than that of beryllium by 10 times or more, the heat of the anode target thin film is efficiently released to the outside through the X-ray transmission window plate. Therefore, a rise in the temperature of the anode target thin film is suppressed, the evaporation of the anode target thin film is reduced, and a long-life transmission radiation X-ray tube is realized.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In this embodiment, the entire surface on the vacuum side of the X-ray transmission window plate 37 is formed into, for example, a spherical surface or a cylindrical surface, and the anode target thin film 39 is formed thereon. In this case, almost the entire anode target thin film 39 is formed concavely with respect to the cathode structure 35. Therefore, even if the anode target thin film 39 thermally expands and generates thermal stress due to the collision of the electron beam, peeling and cracking are prevented as in the above-described embodiment.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. 6, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and duplicate description will be partially omitted.

In this embodiment, the window holding ring 36 is formed thicker than in the embodiment of FIG. And
An opening 51 penetrating through the center of the window holding ring 36 is provided, and a target thin film 39 is adhered on an X-ray transmission window plate 37 attached so as to be exposed at the opening of the opening 51. FIG. 7 shows an enlarged structure of the target thin film 39 portion.

In this case, the inside diameter d of the outside of the opening hole 51 formed in the window holding ring 36, for example, on the X-ray transmission window plate 37 side, is the outside diameter of the concave portion formed on the inner surface of the X-ray transmission window plate 37. For example, the size is set substantially equal to the edge diameter d0.

The inside diameter of the opening hole 51 is d in the X-ray transmission window,
It is formed so as to gradually increase toward the electron gun 34 side. With such a configuration, the focusing of the electron beam is disturbed by the opening hole 51, and the diffusion of the electron beam can be prevented.

Here, a film forming process for forming the anode target thin film 39 on the X-ray transmission window plate 37 will be described with reference to FIG. First, as shown in FIG. 8A, an X-ray transmission window plate 37 is provided on a stepped portion 36b of the window holding ring 36 provided with an opening 51 in advance on the opposite side to the cathode assembly.
Of the metallized peripheral portion 38 of FIG.

Next, the window holding ring 36 to which the X-ray transmission window plate 37 is joined is disposed in the film forming apparatus, and the X-ray transmission window 37 is formed by CVD or the like as shown in FIG. An anode target thin film 39 is formed and adhered to the inner surface with tungsten or the like.

Next, the window holding ring 36 to which the X-ray transmission window plate 37 on which the anode target thin film 39 has been formed is joined,
As shown in FIG. 6, the distal end opening 3 of the metal cylindrical container portion
2a, and the ends of the thin-walled cylinders that match each other are joined in a vacuum-tight manner by heli-arc welding to form a vacuum container. Thereafter, an electron gun or the like is incorporated in the vacuum vessel, and the X-ray tube is completed through an exhaust process and the like.

According to the above configuration, most of the reflected electrons bombard the window holding ring 36 and prevent re-collision with the anode target thin film 39. As a result, the temperature rise of the anode target thin film 39 is reduced, the generation of out-of-focus X-rays is prevented, and the intensity of the electron beam can be further increased to increase the generated X-ray dose.

Further, the anode target thin film 39 is formed so as to extend from the concave surface of the X-ray transmission window plate 37 to the middle of the inner tapered surface of the window holding ring 36, and the entire anode target thin film 39 is formed in a concave shape. Therefore, the effect of preventing peeling and cracking due to thermal stress is enhanced.

In FIGS. 6 to 8, a window holding ring 36 is used as a base component against which reflected electrons impact.
However, the base component having the opening hole 51 is not limited to the window holding ring 36, and other members can be used.
Further, the material of the base component is not particularly limited, but copper or the like is used when the electron beam amount is small. When the electron beam amount is large, it is desirable to use a high melting point metal near the opening near the anode target thin film.

In each of the above embodiments, the anode target thin film is directly attached on the X-ray transmission window plate. However, the present invention is also applicable to a configuration in which the anode target thin film is attached via an intermediate layer such as copper in order to improve the adhesion strength of the anode target thin film.

[0046]

According to the present invention, it is possible to realize a transmission radiation type X-ray tube capable of increasing the intensity of an electron beam to increase the amount of generated X-ray and a method of manufacturing the same.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a portion of an X-ray emission window plate and an anode target thin film used in FIG.

FIG. 3 is a longitudinal sectional view of a main part for describing a manufacturing process of the X-ray emission window plate and the anode target thin film of the present invention.

FIG. 4 is a longitudinal sectional view of a main part showing another embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a portion of an X-ray emission window plate and an anode target thin film used in another embodiment of the present invention.

FIG. 6 is a longitudinal sectional view showing another embodiment of the present invention.

FIG. 7 is an enlarged sectional view showing a main part of FIG. 6;

FIG. 8 is a longitudinal sectional view of a main part for describing a manufacturing process of an X-ray radiation window plate and a target thin film in another embodiment of the present invention.

FIG. 9 is a schematic view showing an X-ray magnification photographing apparatus.

FIG. 10 is a longitudinal sectional view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 30 ... Micro focus transmission radiation type X-ray tube 31 ... Glass container part 32 ... Metal cylindrical container part 33 ... Vacuum container 34 ... Electron gun 35 ... Cathode assembly 36 ... X-ray transmission window plate holding ring 37 ... X-ray transmission window plate 39: anode target thin film 41: concave portion of X-ray transmission window plate 42: concave surface of anode target thin film 51: opening hole of X-ray transmission window plate holding ring

Claims (7)

[Claims] 1. An X-ray transmission window plate hermetically bonded to a part of a vacuum container, and an anode target for directly or indirectly generating X-rays provided on a vacuum-side surface of the X-ray transmission window plate. In a transmission radiation type X-ray tube comprising a thin film and a cathode structure for generating an electron beam for irradiating the anode target thin film, at least a part of the anode target thin film is concave with respect to the cathode structure. Characterized transmission radiation type X-ray tube. 2. An X-ray transmission window plate hermetically bonded to a part of a vacuum vessel, and an anode target for directly or indirectly generating X-rays provided on a vacuum-side surface of the X-ray transmission window plate. In a transmission radiation type X-ray tube comprising a thin film and a cathode structure for generating an electron beam for irradiating the anode target thin film, at least a part of the anode target thin film in a region where an X-ray focus is formed is formed by the cathode structure. A transmission-radiation X-ray tube characterized by having a concave surface. 3. An X-ray transmitting window plate hermetically bonded to a part of a vacuum vessel, and an anode target for directly or indirectly generating X-rays provided on a vacuum-side surface of the X-ray transmitting window plate. In a transmission-radiation X-ray tube including a thin film and a cathode assembly for generating an electron beam for irradiating the anode target thin film, at least a part of the vacuum-side surface of the X-ray transmission window plate is formed as a concave surface. A transmission radiation type X-ray tube characterized by the following. 4. An X-ray transmission window plate hermetically bonded to a part of a vacuum vessel, and an anode target for directly or indirectly generating X-rays provided on a vacuum-side surface of the X-ray transmission window plate. In a method for manufacturing a transmission radiation type X-ray tube comprising a thin film and a cathode assembly for generating an electron beam for irradiating the anode target thin film, at least a part of a surface on the vacuum side of the X-ray transmission window plate has a concave surface. And a second step of directly or indirectly depositing the anode target thin film on the vacuum-side surface of the X-ray transmission window plate having the concave surface formed thereon. Of manufacturing a transmission radiation type X-ray tube. 5. A base component on a vacuum side of an X-ray transmission window plate, the base component being exposed at an opening portion of a through hole, wherein the X-ray transmission window plate is exposed.
4. The transmission radiation type X-ray according to claim 1, wherein the anode target thin film is formed directly or indirectly on the X-ray transmission window plate exposed at the opening of the base component. tube. 6. The transmission / radiation X-ray tube according to claim 5, wherein the inner diameter of the through hole of the base component is formed smaller on the X-ray transmission window plate side than on the cathode assembly side. 7. The X-ray tube according to claim 6, wherein the inner diameter of the through hole of the base component on the side of the X-ray transmission window plate is equal to the diameter of the concave edge of the X-ray transmission window.