JPS6348142B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a target for a large-capacity, high-speed rotating anode X-ray tube.

[Background of the invention]

Conventional targets for large-capacity X-ray tubes include:
(1); A thin plate of tungsten or tungsten alloy (approximately 1 mm) bonded to a molybdenum substrate by forging; (2); The molybdenum substrate of (1) is made thinner and a graphite disk is brazed on the back side. (3) A graphite substrate coated with tungsten or a tungsten alloy, but none of these methods were suitable for high-speed rotation. In other words, the structure (1) has high mechanical strength, but if it is made to have a large capacity, the weight increases, and the structure (2) does not have a very strong joint strength between molybdenum and graphite. Moreover, the weight of the molybdenum substrate itself is still quite large. On the other hand, structure (3) has the advantage of using low-density graphite, which makes it easy to construct a target that is relatively lightweight and has a large heat capacity, but graphite has low mechanical strength and will break when rotated at high speeds. Therefore, it was not possible to use a large-diameter target at high speed.

[Purpose of the invention]

The present invention was made in view of these circumstances, and its purpose is to provide a lightweight and mechanically strong material.
An object of the present invention is to provide a large-capacity X-ray tube target suitable for high-speed rotation.

[Summary of the invention]

In order to achieve such an objective, the present invention
A ceramic disk with high thermal conductivity is used, a graphite layer is bonded to the top surface, the outer circumference of the top surface is sloped, and the slope is coated with tungsten or a tungsten alloy.

That is, a ceramic substrate is used to obtain mechanical strength, and graphite is interposed therebetween in order to firmly adhere tungsten or a tungsten alloy to the ceramic. Ceramic material has about 10 times the strength as graphite material and also has a high Young's modulus, so centrifugal stress and other mechanical stresses are applied to the ceramic material. In addition, in order to efficiently dissipate the heat generated by the impact of accelerated electrons, it is necessary for such ceramic materials to have high thermal conductivity equivalent to that of metals, and for this purpose materials such as BeO-doped SiC are used. suitable. The adhesion of tungsten or tungsten alloy coatings is better with graphite materials than with ceramic materials, so the interposition of graphite material makes the coating process easier and makes it easier to coat when used. The reliability of the system is also improved. Hereinafter, the present invention will be explained in detail using examples.

[Embodiments of the invention]

FIG. 1 is a sectional view showing one embodiment of the present invention. In the figure, graphite layers 2 and 3 having electrical conductivity are stacked and bonded to the upper and lower surfaces of a disk-shaped ceramic substrate 1 having high thermal conductivity, respectively.
Regarding the graphite layer 2 on the upper surface side, a portion of the outer periphery of the upper surface where the electron beam collides is formed into an inclined surface, and a coating layer 4 made of tungsten or a tungsten alloy is provided on this inclined surface. 5 indicates a rotor joint hole. Coating is carried out, for example, by a CVD method, but it is better to coat the surface of the graphite layer 2 with a thin layer of rhenium in advance and then coat a tungsten or tungsten alloy layer than to coat the graphite surface directly. The strength is high. Further, the thickness of the tungsten or tungsten alloy layer is suitably about 600 μm or less, since if it is too thick, it will be difficult to adhere or break easily. As for the tungsten alloy, one containing 1 to 20% rhenium is practically preferable because the focal orbital surface is less rough during use.

To bond and bond the ceramic substrate 1 and the graphite layers 2 and 3, when processing the ceramic substrate 1 by hot pressing, the ceramic material is sandwiched from the upper and lower surfaces between graphite plates in a mold, and the whole is vacuumed. By holding the ceramic substrate at a high temperature inside and applying pressure to the graphite plate, the ceramic substrate 1 is formed and, at the same time, graphite layers are adhered to its upper and lower surfaces.

In the above structure, as mentioned above, the graphite layer 2 on the top side of the ceramic substrate 1 plays the role of ensuring the adhesive strength of the coating layer 4 made of tungsten or tungsten alloy, but the graphite layer 2 on the bottom side The graphite layer 3 serves to promote the dissipation of heat generated by the collision of the electron beam and stored inside the ceramic substrate 1 to the outside.

Note that when the ceramic substrate 1 is made of a black material such as BeO-doped SiC, the ceramic material can be left exposed on the lower surface of the target because it itself has a high thermal emissivity and good heat radiation.

FIG. 2 is a sectional view showing another embodiment of the invention. In this embodiment, a ceramic substrate is formed of two layers 1a and 1b, with a graphite layer 6 inserted between them.

Similarly, FIG. 3 is a sectional view showing another embodiment of the present invention. In this embodiment, a ceramic substrate 11 itself has a sloped surface on its outer periphery, and as the graphite layers 12 and 13 to be bonded to the upper and lower surfaces, a graphite plate having a sloped surface on its outer periphery is used. As described above, it can be easily formed by sandwiching and pressing the ceramic material.

〔Effect of the invention〕

As explained above, according to the present invention, by using a ceramic substrate that has about 10 times the strength compared to graphite, the strength as a target is improved, and the density is about 1.6 compared to graphite. Although it increases by ~1.8 times, it can be significantly lighter compared to those using metal substrates such as molybdenum, and it is lightweight and has high strength.
An optimal target for large-capacity, high-speed rotating anode X-ray tubes can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIG.
3 and 3 are sectional views showing other embodiments of the present invention, respectively. 1, 1a, 1b, 11...ceramic substrate,
2, 3, 6, 12, 13... graphite layer, 4
...A coating layer made of tungsten or tungsten alloy.

Claims (1)

[Claims] 1. An X-ray tube target comprising a graphite layer laminated on at least the upper surface of a circular plate made of ceramic with high thermal conductivity, and a tungsten or tungsten alloy layer laminated on an inclined surface provided on the outer periphery of the upper surface of the graphite layer. .