JPH0793100B2 - Method of manufacturing target for X-ray tube - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an X-ray target used for an X (hereinafter referred to as X) ray tube.

An X-ray tube using an X-ray target according to the present invention is suitable for use in an X-ray sheet (hereinafter referred to as CT. Abbreviation of Computed Tomography) apparatus for medical equipment.

[0003]

2. Description of the Related Art An example of a rotary anode X-ray target used for an X-ray tube is described in Japanese Patent Publication No. 47263 / 47-8263. In this patent publication, an X-ray target having a structure in which a graphite is used as a base and a tungsten / rhenium alloy coating is applied only in the vicinity of a portion irradiated with an electron beam, and an intermediate of rhenium between the graphite base and the tungsten / rhenium alloy coating. An X-ray target with a layered structure is shown. An X-ray target having such a structure is described to protect the tungsten-rhenium alloy coating from thermal overload due to the large heat capacity of graphite.

JP-A-60-202643 discloses a structure of an X-ray tube equipped with an X-ray target.
Further, JP-A-61-183861 discloses an example of the structure of an X-ray tube containing an X-ray tube.

[0005]

The properties required of the X-ray CT apparatus for medical equipment include shortening the diagnosis time and sharpening the processed image.

In order to meet these requirements, it is necessary to increase the input of the X-ray tube and increase the X-ray radiation amount.

The X-ray target receives an electron beam from the cathode to generate an X-ray, but most of the electron beam is converted into heat when the X-ray is generated, and the X-ray target is heated to a high temperature. To be done. The heating temperature of the X-ray target rises as the input is increased.

According to the result of examination by the present inventor, Japanese Patent Publication No. 47-
As in the invention described in Japanese Patent No. 8263, in which the X-ray target substrate is made of graphite and the portion where the electron beam collides is coated with the X-ray generating metal material, the The thermal conductivity is poor, and when the input increases, the X-ray generating metal coating easily separates from the graphite substrate.

As described above, the conventional X-ray target cannot effectively utilize the large heat capacity of graphite.

An object of the present invention is to provide an X-ray target having good adhesion between the X-ray generating metal coating and the graphite substrate and capable of rapidly transferring heat generated in the X-ray generating metal coating to the graphite substrate. Providing a manufacturing method.

Still another object of the present invention is to provide an X-ray tube and an X-ray tube equipped with such an X-ray target.

[0012]

The present invention provides a method for producing an X-ray target, which comprises a step of forming an X-ray generating metal coating layer on an electron beam irradiation surface on a graphite substrate, and a graphite substrate before the step. At the interface with the X-ray-generating metal coating layer, a metal intermediate layer that is non-reactive with graphite and has a coefficient of thermal expansion approximately equal to that of the graphite and X-ray-generating metal coating is chemically treated under normal pressure or a pressure near normal pressure. It is characterized in that it is formed by vapor plating. After coating this metal intermediate layer, it can be produced by coating the X-ray generating metal by means such as chemical vapor deposition, sputtering or thermal spraying.

By performing chemical vapor deposition under atmospheric pressure or a pressure around atmospheric pressure, it becomes possible to permeate the metal intermediate layer into the inside of the graphite substrate.

[0014]

In the X-ray target obtained by the production method of the present invention, the X-ray-generating metal coating layer is less likely to peel off than the conventional X-ray target described above, but this effect is due to the fact that the metal intermediate layer is inside the graphite substrate. It is based on having penetrated to.

By infiltrating the metal intermediate layer into the inside of the graphite substrate, the contact area between the two is remarkably increased, and the heat generated in the X-ray generating metal coating layer is rapidly transferred to the graphite substrate. Moreover, the metal intermediate layer that has penetrated into the graphite substrate functions as a wedge, and makes it difficult for the X-ray generating metal coating layer to separate from the graphite substrate.

According to the experiments conducted by the present inventors, when the metal intermediate layer is not permeated into the graphite substrate, the tube voltage and the tube current at which the X-ray-generating metal coating layer can be flowed to the X-ray tube without being peeled off. Was about 120 KV and 350 mA.
On the other hand, in the case where the metal intermediate layer is infiltrated into the inside of the graphite substrate, a tube voltage of 120 KV and a tube current of 600 mA can be applied.

(A) Structure of X-ray target In the X-ray target of the present invention, the substrate is made of graphite. The graphite substrate has a large heat capacity as compared with a metal, has good thermal conductivity, and is lightweight. The advantage of being light in weight is that it can be used by simply incorporating the X-ray target of the present invention into the X-ray tube having the structure described in JP-A-60-202643, and the tube input can be increased. Bring effect.

The graphite substrate does not necessarily have to consist of graphite. It may be a mixture of graphite and metal powder and sintered. For example, a substrate made of a sintered body of graphite and tungsten powder has good thermal conductivity and strength, and can be sufficiently used as the substrate of the X-ray target according to the present invention. The amount of the metal powder in the case of forming a sintered body of graphite and the metal powder should be determined so that the heat capacity of the graphite itself is not significantly impaired. The amount of graphite should be at least above 50% by volume.

The substrate may have a laminated structure by stacking a graphite thin plate and a thin plate made of another member. As the other member in this case, metal or ceramic can be used. The strength of the base can be increased by stacking the thin plate of graphite and the thin plate of the thermally conductive silicon carbide sintered body to form the base.

The material of the X-ray generating metal coating layer that covers the vicinity of the portion of the graphite base on which the electron beam collides is selected from those having a high melting point so as not to dissolve even when irradiated with the electron beam. The x-ray generating metallization layer is approximately 250 in most cases.
It is heated to around 0 ° C. Therefore, it is desirable to select a metal having a high melting point of 2500 ° C. or higher and generating X-rays. Tungsten or a tungsten-rhenium alloy is particularly suitable as a material for the X-ray generating metal coating layer. Although rhenium can be used alone, it is inferior to tungsten or a tungsten-rhenium alloy and is very expensive.

Graphite and tungsten easily react with each other to form a carbide. Therefore, if the graphite or the tungsten-rhenium alloy is directly coated on the graphite substrate, brittle carbides are generated at the interface between the two and are easily separated.

For this reason, it is necessary to interpose a metal that does not or hardly reacts with graphite in the middle of the two. This metal is also preferably selected from those having a high melting point, specifically, a melting point of 2500 ° C. or higher so as not to be melted by electron beam irradiation.

Rhenium is the best material for the metal intermediate layer. The thermal expansion coefficient of rhenium is also close to that of graphite, so that thermal stress is unlikely to concentrate at the interface between graphite and rhenium.

The metal intermediate layer needs to penetrate into the pores on the surface of the graphite substrate and penetrate to the inside. By infiltrating the metal intermediate layer into the inside of the graphite substrate as described above, it is possible to make it difficult to peel off the X-ray generating metal coating layer, as described above, and increase the input load on the X-ray tube to shorten the diagnosis time. Also, the processed image can be sharpened. 1 and 2 are sectional views showing an embodiment of an X-ray target obtained by the manufacturing method of the present invention. FIG. 1 is an enlarged view of the vicinity of a portion hit by an electron beam, and FIG. 2 is a schematic view of the entire X-ray target.

An X-ray generating metal coating layer 2 covers a part of the surface of the graphite substrate 1, a metal intermediate layer 3 is interposed between the two, and penetrates into the graphite substrate 1.

The metal intermediate layer 3 has a penetration depth of 10 mm between the surface of the graphite substrate and the tip of the penetration part of the metal intermediate layer.
It is preferable to manufacture it so as to have a thickness of μm or more.

If the penetration depth of the metal intermediate layer is small, the X-ray-generating metal coating layer is likely to peel off, increasing the load input of the X-ray tube and shortening the diagnosis time or making it difficult to sharpen the processed image. .

In order to enable detailed diagnosis of blood vessels and the like in the X-ray CT apparatus, an X-ray target having a heat capacity of 1500 to 2000 kilo heat unit (KHU) or more is required. Penetration depth of metal intermediate layer is 10μ
By setting m or more, this requirement can be sufficiently satisfied.

The thickness of the X-ray generating metal coating layer 2 should be larger than the depth at which the electron beam enters. Since the depth at which the electron beam enters is approximately 10 to 15 μm, the depth of the X-ray generating metal coating layer is preferably 20 μm or more. Making the X-ray generating metal coating layer thicker than necessary causes an increase in the weight of the X-ray target and causes wear of the bearing when rotating at a high speed, which causes rotation blurring and the like. From this, it is desirable that the thickness of the X-ray generating metal coating layer is limited to about 500 μm at the maximum, and it is particularly desirable to set the thickness to about 50 to 200 μm.

Of the total thickness of the metal intermediate layer, the thickness of the portion covering the surface of the graphite substrate is 3 μm or more, usually 5 to 5.
10 μm is sufficient. The metal intermediate layer acts as a barrier for preventing the formation of a brittle carbide layer on the graphite substrate, and this action can be sufficiently achieved if the thickness of the metal intermediate layer covering the surface of the graphite substrate is 3 μm. When the thickness of the metal intermediate layer is small, the graphite diffuses inside the layer and reacts with the X-ray generating metal coating layer, and the reaction product carbide is formed between the metal intermediate layer and the X-ray generating metal coating layer. May be generated at the interface of. However, the presence of the carbide in this case does not impair the adhesiveness between the X-ray generating metal coating layer and the metal intermediate layer. Therefore, the formation of such a carbide layer does not matter.

In order to improve the thermal conductivity from the X-ray generating metal coating layer to the graphite substrate, it is desirable that the X-ray generating metal coating layer has a columnar crystal structure. Such a columnar crystal structure can be easily obtained by coating using a chemical vapor deposition technique.

However, in the case of the columnar crystal structure as described above, fine cracks are likely to occur due to the collision of electron beams, and there is a possibility that the cracks may propagate and lead to X-ray weight loss. For this reason, it is desirable that the X-ray generating metal coating layer has two layers, the outermost surface layer on which the electron beam strikes has a fine structure, and the lower part thereof has a columnar crystal structure. The microstructure of the outermost surface layer is finer than that of the columnar crystals below it.

The outermost surface layer of the fine structure can be obtained by controlling the set conditions for chemical vapor deposition,
It can also be obtained by using a method of sputtering or thermal spraying.

Pure metals generally have better thermal conductivity than alloys. On the other hand, when an alloy is used, the recrystallization temperature is generally higher than that of pure metal, and it becomes possible to endure a higher temperature when an electron beam is incident. From this, it is desirable that the outermost surface layer is formed of an alloy and the columnar crystals below the outermost layer are formed of a pure metal. In order to realize an X-ray target having a high heat capacity and a high thermal conductivity, it is necessary to form an X-ray generating metal coating layer having a two-layer structure consisting of an outermost surface layer made of a tungsten-rhenium alloy and a pure tungsten columnar crystal thereunder. Highly desirable. In this case, the composition of the tungsten-rhenium alloy is preferably such that rhenium is 1 to 10% by weight and the balance is tungsten.

FIG. 3 shows a partial sectional view of an X-ray target of the present invention having an X-ray generating metal coating layer having a two-layer structure. The X-ray generating metal coating layer 2 includes an outermost surface layer 4 and a lower columnar crystal layer 5. Reference numeral 1a indicates pores in the graphite substrate 1. When the two-layer structure is used, the total thickness of the X-ray generating metal layer is preferably 20 to 500 μm, of which the outermost surface layer has a thickness of 50 to 200 μm and the lower columnar crystal layer has a thickness of 50 to 300 μm. The degree is desirable.

FIG. 4 shows an example in which the graphite substrate 1 has a structure in which three plates are laminated, and one of them is a ceramics sintered plate. In FIG. 4, reference numeral 6 is a graphite plate, and a ceramic sintered body 7 is sandwiched between two graphite plates. As the ceramics sintered body, it is desirable to use one having good thermal conductivity, for example, a silicon carbide sintered body containing beryllia. With such a structure in which the sintered ceramics are sandwiched, the mechanical strength of the graphite substrate can be increased.

(B) Method for manufacturing X-ray target The graphite substrate of the X-ray target can be manufactured by sintering. The graphite substrate produced by sintering has many pores as it is, and has a requirement of the graphite substrate in the X-ray target of the present invention, that is, a requirement of being a porous graphite substrate.

When it is desired to further increase the number of pores near the surface of the graphite substrate, the surface may be roughened by heating in the air and then immersing in hot water, or by immersing in a chemical to artificially. You may make a hole in. Any other suitable pore forming means may be used, and the method is not limited to the above method.

Since the metal intermediate layer must penetrate into the pores near the surface of the graphite substrate, it is necessary to form it by chemical vapor deposition under atmospheric pressure or a pressure in the vicinity of atmospheric pressure. In the method using sputtering or thermal spraying, it is difficult to set the penetration depth of the metal intermediate layer to 10 μm or more.

In an experiment in which a metal intermediate layer was formed with a chemical vapor deposition (also referred to as CVD or chemical vapor deposition) pressure of 10 ^-2 Torr, the metal intermediate layer was sufficiently penetrated into the inside of the graphite substrate. I couldn't. Therefore, it is necessary to perform the chemical vapor deposition at a pressure near normal pressure. A suitable atmospheric pressure is atmospheric pressure. Treatment under reduced pressure, which is a high vacuum, should be avoided as it impedes the penetration of the metal intermediate layer into the graphite substrate.

When the metal intermediate layer is formed by chemical vapor deposition, it is desirable to heat the graphite substrate, and the maximum penetration depth is significantly affected by this heating temperature. The preferred heating temperature for the graphite substrate is 200 to 300 ° C.
Is. If the heating temperature is low and the thermal decomposition is low, the thermal decomposition is difficult to proceed, and the metal intermediate layer cannot be sufficiently formed and penetrated into the inside of the graphite substrate. If the heating temperature is too high, thermal decomposition proceeds only on the surface of the graphite substrate, and the metal intermediate layer is deposited on the surface of the graphite substrate and does not penetrate inside.

The X-ray generating metal coating layer is formed by chemical vapor deposition,
It is preferably formed by sputtering or thermal spraying. When forming a columnar crystal structure, it is desirable to perform chemical vapor deposition. When obtaining a fine structure, it is convenient to perform sputtering or thermal spraying.

When the X-ray generating metal coating layer has a two-layer structure and the outermost surface layer having a fine structure and the columnar crystal layer thereunder are formed in a single step, chemical vapor deposition is adopted, and This can be achieved by controlling the composition, pressure, temperature, reducing gas, etc. of the coating layer forming gas when forming the surface layer.

(C) Structure of X-ray tube and X-ray tube FIG. 5 is a schematic sectional view of an X-ray tube according to an embodiment using an X-ray tube target obtained by the manufacturing method of the present invention. 6 shows a schematic sectional view of the rotary anode.

The X-ray tube 10 has an X-ray tube 100 built in a closed container 11. A cooling medium 15 is filled around the X-ray tube 100 in this container.

The closed container 11 has an X-ray radiation window 12. It is desirable that the X-ray emission window 12 has a lead slit formed on the outer surface or the inner surface of the glass plate, leaving a portion for emitting X-rays. It is desirable that an X-ray shielding material, for example, a lead plate is also placed inside the closed container except the X-ray radiation 12.

The X-ray tube generates a large amount of heat together with X-ray radiation as described in JP-A-61-183861. In order to forcibly cool the generated heat, the cooling medium 15 is filled and circulated in the closed container. A liquid medium such as oil is often used as the cooling medium.

The X-ray tube 100 has a rotating anode 120 and a cathode 130 inside a vacuum tube 110. The vacuum tube 110 is usually a glass tube. The rotating anode 120 includes an X-ray target 121 and a rotating mechanism for the X-ray target. The rotating mechanism of the X-ray target includes a motor / rotor, and has a motor / stator 125 at a position facing the rotor outside the X-ray tube. Regarding the rotating mechanism of the X-ray target, a structure very similar to that of the present invention is described in considerable detail in JP-A-61-183861.

The cathode 130 has a filament for emitting an electron beam, and the emitted electron beam 131 is incident on the X-ray target 121 and the X-ray emission window 12 of the closed container 11.
Emitted from. Reference numeral 129 indicates an anode terminal, and reference numeral 1
Reference numeral 39 indicates a cathode terminal. Also, reference numerals 141 and 142
Shows a cushion that prevents the X-ray tube 100 from colliding with and damaging the closed container 11. Code 11
Reference numeral 1 denotes a portion in which the inside of the vacuum tube is vacuumed and finally the tube end is sealed, that is, a vacuum sealing portion.

In FIG. 5, a rubber lid 1 is attached to the upper end of the closed container 11.
It is covered with 3. This is to prevent the cooling medium from leaking out of the tube even when the X-ray tube is broken for some reason. The rubber lid 13 prevents the cooling medium from flowing out due to the elastic action of the rubber.

The rotary anode 120 comprises an X-ray target 121 and its rotating mechanism as shown in FIG. The rotating mechanism has a rotating shaft 122 and a cylindrical rotor 123. Copper is suitable as the material of the rotor 123. The circumference of the rotating shaft 122 is surrounded by the fixed shaft 124,
A bearing 126, specifically, a ball bearing is provided between the rotary shaft and the fixed shaft. Reference numeral 127 is a stopper of the bearing 126. Further, reference numeral 128 is a spacer between the rotor 123 and the fixed shaft 124. The fixed shaft 124 includes the fixed member 15
It is fixed at 0.

Regarding the structure of the X-ray tube and the rotating anode,
Japanese Patent Laid-Open No. 60-202643 also discloses a structure similar to the present invention.

In order to shorten the diagnosis time by the X-ray CT apparatus and sharpen the processed image, it is necessary to enlarge the X-ray target and increase the heat capacity. However, when the X-ray target becomes large and the weight increases, the load applied to the bearing increases, and abrasion powder is generated from the sliding portion with the rotating shaft, so that the rotating shaft becomes eccentric. In addition, the generation of abrasion powder lowers the withstand voltage, which may make it unusable.

Therefore, when a large X-ray target is used, it is necessary to develop a rotating anode suitable for it or to improve the rotating mechanism. However, the X-ray target of the present invention is based on graphite, and the heavy X-ray generating materials such as tungsten and rhenium are used only on a small part of the surface of the target, and therefore, the structure shown in FIG. 6 is used. It can be used by being incorporated in a rotating anode and can exhibit a high heat capacity.

It is extremely epoch-making in that it can be used by incorporating it into a conventional rotary anode having a very general structure, and that a high heat capacity can be achieved.

[0056]

【Example】

(Example 1) A target having graphite as a substrate, rhenium as an intermediate layer, tungsten as an underlayer of an X-ray generating metal material, and a tungsten-rhenium alloy as the outermost surface was experimentally manufactured. Figure 3
Is the cross-sectional structure near the target surface. The graphite base 1 has a large number of holes 1a. The metal intermediate layer 3 penetrates into the holes 1a in the surface portion of the graphite substrate 1 to form a layer, and has the X-ray generating metal coating layer 2 having a two-layer structure thereon. In order to manufacture this target, first, the graphite substrate 1a is machined, ultrasonic cleaning is performed with pure water to remove the clogging of the pores 1a of cutting powder generated at that time, and the target is vacuumed at 1500 ° C. It was heat-treated by baking in. After that, the rhenium layer of the metal intermediate layer 3, the columnar crystal tungsten layer 5 and the fine crystal tungsten-rhenium alloy layer 4 as the X-ray generating metal coating layer 2 were continuously provided in a single step by chemical vapor deposition.

The composition of the tungsten-rhenium alloy is 5% by weight of rhenium with the balance being tungsten. This alloy layer has a thickness of 100 μm, and the tungsten layer has a thickness of 200 μm.
m. The thickness of the rhenium layer interposed on the surface of the graphite substrate was about 10 μm, and the maximum penetration depth into the inside of the graphite substrate was about 100 μm. The chemical vapor deposition was carried out by a method of reducing rhenium fluoride and tungsten with hydrogen under normal pressure, but the deposition conditions of both rhenium fluoride and tungsten fluoride differ depending on the temperature and pressure. Therefore, the substrate temperature was adjusted to about 300 ° C. so that rhenium in the metal intermediate layer 3 could sufficiently penetrate into the surface pores 1a of the graphite substrate 1, and plating was performed.
On the other hand, although tungsten has a wide deposition temperature, the higher the temperature, the larger the grain size of the columnar crystals and the larger the surface irregularities.
In addition, the grain size morphology of the tungsten-rhenium alloy changes with temperature. Therefore, this time, columnar crystals of tungsten 5 at a substrate temperature of about 550 ° C. and fine crystals 4 of a tungsten-rhenium alloy at a substrate temperature of about 450 ° C. are provided on the metal intermediate layer 3. The target thus obtained is lightweight, has a large heat emissivity and a large heat capacity, and has a strong bond between the graphite substrate 1 and the metal intermediate layer 3 even under severe conditions of use, so that the target of peeling and thermal conductivity can be improved. There is no problem such as deterioration.

FIG. 7 shows the X-ray reduction and scanning when this X-ray target and a conventional target were incorporated into an X-ray tube having the structure shown in FIG. 5 to generate X-rays at a tube voltage of 120 KV and a tube current of 400 mA. It is a characteristic view related to the number.

As a conventional target, a graphite base target in which a tungsten / rhenium layer is provided on a graphite substrate via a rhenium layer and a structure in which the rhenium layer does not permeate is provided, and a tungsten.
A metal target formed by sintering a rhenium alloy layer was used.

In FIG. 7, a voltage of 120 KV and a current of 40
Looking at the change in the X-ray dose of the target under the use condition of 0 mA, the target of the present invention shows less X-ray reduction than the graphite-based target without penetration of the rhenium layer and the metal target. The target of the present invention has a voltage of 120K.
No change was observed even when a large load of V and a current of 600 mA was applied.

(Example 2) In Example 1, the same effect was obtained by using fine tungsten of fine crystal instead of the tungsten-rhenium alloy of the outermost layer.

(Embodiment 3) As described above, the target should not cause peeling of the metal intermediate layer and the X-ray generating metal coating layer due to thermal stress. Therefore, the film forming method of the metal intermediate layer and the adhesion to the graphite substrate were examined. One is the sputtering method and the other is the chemical vapor deposition method.
First, as a sputtering method, a rhenium film was formed by a sputtering down method in which a rhenium target for sputtering having a purity of 99.9% or more was placed on the upper side and a graphite substrate was placed on the lower side. The sputtering gas is argon, the pressure is 0.01 Torr, and the rhenium is 1
A film was formed by sputtering on a graphite substrate having a thickness of about 0 μm. as a result,
No penetration of rhenium into the pores specific to the graphite substrate was observed. In addition, a swelling phenomenon was often observed on a high-density graphite substrate with few stains and voids, which was formed by sputtering by vacuum heat treatment at 1000 to 1500 ° C. Therefore,
When providing the intermediate layer by the sputtering method, it is necessary to pay particular attention to the pretreatment method of the substrate.

Next, in chemical vapor deposition, for example, when rhenium fluoride is deposited by a hydrogen reduction method under atmospheric pressure, the permeation state of rhenium into the pores of the graphite substrate and the deposition rate, and the film quality thereof depend on the temperature. different. For example, if the temperature is set to about 200 to 300 ° C., a rhenium film that has sufficiently penetrated into the surface pores of the graphite substrate can be obtained. At 400 ° C., rhenium is deposited thickly on the graphite substrate, but the penetration into the pores is insufficient. Is. When the temperature further rises to 500 ° C., powdery rhenium is deposited, which makes the intermediate layer unsuitable. Therefore, the windowing property between the intermediate layer and the graphite substrate is
It is suitable to use a chemical vapor deposition method at a temperature of 200 to 300 ° C.

(Embodiment 4) It is conceivable to use a composite substrate in which the heat capacity is graphite and the rotation speed is metal, ceramic or the like. Then, the target shown in FIG. 4 was prototyped. The composite substrate is a laminated body of silicon carbide (SiC) sintered plate 7 containing beryllia (BeO), which is known as a high thermal conductive ceramic, and a graphite plate 6, and when SiC is sintered by hot pressing, Graphite and Si used as spacers
What was firmly adhered with C was processed into a target shape. Then, it was washed with pure water and heated at 1500 ° C. under vacuum to provide the metal intermediate layer 3 with the rhenium and X-ray generating metal coating layer 1 by chemical vapor deposition. The X-ray generating metal coating layer 1 at this time was a fine single crystal layer of tungsten / rhenium. With this target as well, the same effect as in Example 1 was obtained, and the rotational rupture strength could be doubled or more.

Graphite has amorphous pores locally or wholly and at the same time, reacts with many metals to form a hard and brittle compound. Therefore, the intermediate layer of the target is selected from high-melting-point metals that are difficult to form compounds. However, since they are different materials, large thermal stress concentrates on the interface during actual load. Therefore, as in the present invention, if the intermediate layer penetrates and bonds to the holes originally possessed by the substrate, the thermal conductivity is not impaired, and thus the conventional problem of delamination of the X-ray generating material due to thermal stress is eliminated. Since this can be prevented, it is possible to manufacture a highly reliable target. This target has a weight of 1/3 or less as compared with a metal target of the same shape, and a target having a heat capacity of 2 times or more can be formed. Therefore, according to the present invention, a large current due to the electron beam can be input, so that the X-ray image can be made clearer and the diagnostic efficiency can be improved (the imaging time can be shortened).

[0066]

As described above, in the X-ray tube target obtained by the manufacturing method of the present invention, the X-ray-generating metal coating layer is unlikely to peel off and the thermal conductivity from the coating layer to the graphite substrate is good. Therefore, it is suitable as a high heat capacity X-ray target.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view of a schematic sectional view of an X-ray target according to an embodiment obtained by a manufacturing method of the present invention.

FIG. 2 is an overall sectional view of a schematic sectional view of an X-ray target according to an example obtained by the manufacturing method of the present invention.

FIG. 3 is a partially enlarged sectional view of an X-ray target according to another embodiment of the present invention.

FIG. 4 is a sectional view of an entire X-ray target according to another embodiment of the present invention.

FIG. 5 is a schematic sectional view showing an embodiment of the X-ray tube of the present invention.

FIG. 6 is a schematic cross-sectional view showing an embodiment of the rotating anode of the present invention.

FIG. 7 is a characteristic diagram showing the relationship between the number of scans and X-ray reduction when using an X-ray tube incorporating various X-ray targets.

[Explanation of symbols]

1 ... Graphite substrate, 2 ... X-ray generating metal coating layer, 3 ... Metal intermediate layer, 10 ... X-ray tube, 100 ... X-ray tube, 120 ... Rotating anode, 121 ... X-ray target.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masatake Fukushima Inventor Masatake Fukushima 4026 Kuji Town, Hitachi City, Ibaraki Hitachi Ltd., Hitachi Research Laboratory (72) Inventor Masateru Suwa 4026 Kuji Town, Hitachi City, Ibaraki Hitachi Research Institute, Ltd. In-house (72) Inventor Ichiro Inamura 1-14-1 Uchikanda, Chiyoda-ku, Tokyo Hitachi Medical Co., Ltd. (56) References JP-A-53-102690 (JP, A) JP-A-57-61252 (JP) , A)

Claims (6)

[Claims] 1. A method of manufacturing a target for an X-ray tube, which comprises a step of coating an electron beam irradiation surface on a substrate made of a graphite sintered body with an X-ray generating metal, and graphite is provided on the surface of the graphite substrate before the step. Including a step of forming a non-reactive metal intermediate layer by performing chemical vapor deposition under a pressure near normal pressure and permeating the graphite and a non-reactive metal into the graphite base pores , Lower layer of columnar structure and fine assemblage
X-ray generating metal coating layer of laminated structure consisting of the outermost surface layer of woven fabric
A method for manufacturing a target for an X-ray tube, which is characterized in that the target is formed sequentially . 2. The method for producing an X-ray tube target according to claim 1, wherein the X-ray generating metal is a tungsten-rhenium alloy or tungsten, and the metal intermediate layer is rhenium. 3. The chemical vapor deposition temperature is 200 to 300.
The method for producing a target for an X-ray tube according to claim 1 or 2, which is at a temperature of ° C. 4. A method for producing a target for an X-ray tube, which comprises a step of coating an electron beam irradiating surface on a graphite substrate with an X-ray generating metal, under the condition that a pressure near atmospheric pressure is satisfied before the step. A step of coating the surface of the graphite substrate with a rhenium layer by chemical vapor deposition and permeating rhenium into the graphite substrate, and thereafter forming a two-layer structure comprising a lower tungsten layer and an outermost surface layer of a tungsten-rhenium alloy. A method of manufacturing a target for an X-ray tube, which comprises sequentially forming an X-ray generating metal coating layer having a structure. 5. The method for producing a target for an X-ray tube according to claim 4, wherein the tungsten lower layer is formed into a columnar crystal structure by chemical vapor deposition. 6. The method for producing an X-ray tube target according to claim 4, wherein the outermost surface layer of tungsten / rhenium is formed into a fine structure by any one of chemical vapor deposition, sputtering and thermal spraying.