JPH04154029A - X-ray image tube - Google Patents

Abstract

PURPOSE:To obtain a required structure without unnecessarily enlarging the thickness of a plate and a meridian curvature radius of an input window by making the peripheral part of the meridian curvature radius smaller than the central part so as to improve intensity of the input window. CONSTITUTION:The peripheral part 10b of the curvature radius of an input window 10 connected airtight to the open end of a bottomed cylindrical envelope main body 2, in the direction of meridian is defined smaller than the center part 10a. Namely, Rc>Re is satisfied, where Rc is the curvature radius in the center part 10a of the input window 10, and Re is the curvature radius in the peripheral part 10b. The intensity of the input window is thus improved. A required structure is thus obtained without unnecessarily enlarging the plate thickness of the input window 10 and a meridian curvature radius, and the reliability and performance of a product can be improved, while the size and the weight thereof can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) This invention relates to an X-ray image tube, and more particularly to an improvement in the input window of its vacuum envelope.

(Prior Art) Conventionally, an X-ray image tube is configured as shown in FIG.
The vacuum envelope 1 includes a bottomed cylindrical envelope body 2 made of metal or glass, and an input window 3 hermetically sealed to the open end of the envelope body 2.
It consists of In this case, the input window 3 is formed so that the radius of curvature in the meridian direction is the same at both the center and the periphery. In other words, the radius of curvature is the same over the entire surface.

On the input side of such a vacuum envelope 1, an input surface 4 is arranged opposite to the input window 3. On the other hand, vacuum envelope 1
On the output side of the vacuum envelope 1, an anode 5 is arranged and an output surface 6 is formed, and a focusing electrode 7.8 is arranged along the side wall of the vacuum envelope 1.

During operation, the X-rays emitted from the X-ray generator strike the object (
(not shown) and reach the input surface 4, and the photoelectrons emitted from the input surface 4 are focused by the focusing electrode 7.8 and the anode 5.
The acceleration excites the output surface 6, on which a light output image with enhanced brightness is reproduced.

By the way, in order to improve the reliability of this type of X-ray image tube in its manufacturing process, it is necessary to maintain vacuum tightness between the envelope body 2 and the input window 3.

This vacuum sealing is achieved by welding or pressure welding, for example, but the input window 3 is designed to minimize X-ray transmittance and scattering of X-rays by the input window material, and to provide sufficient strength as the vacuum envelope 1. should be considered to ensure that the

(Problem to be Solved by the Invention) When considering the structure of the input window 3 as the vacuum envelope 1, it goes without saying that a spherical surface is better from the viewpoint of strength. However, the radius of curvature in the meridian direction should be small, the plate thickness should be thick,
As for the material, it goes without saying that an aluminum alloy is stronger than pure aluminum metal, and furthermore, for example, a stainless steel alloy is even stronger.

However, for X-ray transmittance, it is better to make the plate thinner, and it is better to select a material with a small atomic number. Furthermore, in terms of downsizing the X-ray image tube, the input window 3 having a large meridional curvature radius is better than the input window 9 having a small meridional curvature radius as shown in FIG. In this way, it is necessary to carefully consider the structure of the input window that satisfies the mutually contradictory properties.

An object of the present invention is to provide an X-ray image tube that has an input window that maintains sufficient strength, has high X-ray transmittance, has low scattering, is compact, and has improved reliability as a product. do.

[Structure of the Invention (Means for Solving the Problems) This invention provides a manual window which is airtightly connected to the open end of a bottomed cylindrical envelope main body, so that the radius of curvature in the meridian direction is larger than the center part. This is an X-ray image tube with a smaller size.

(Function) According to the present invention, the required structure can be obtained without unnecessarily increasing the board thickness or meridional curvature radius of the input window, and the reliability and performance of the product are improved. Weight reduction can be achieved.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

The X-ray image tube according to the present invention is constructed as shown in FIG. An input window 10 is hermetically sealed to the open end of the vacuum envelope 11 by TIG welding or pressure welding, thereby forming a vacuum envelope 11.

In this case, the radius of curvature of the human powered window 10 in the meridian direction is
The peripheral portion 10b is set smaller than the central portion 10g. That is, if the radius of curvature at the central portion 10a of the input window 10 is Re, and the radius of curvature at the peripheral portion 10b is Re, the setting is made to satisfy the relationship Rc>Re.

Here, if aluminum is used as the material for the input window 10, the thickness of the input window 10 can be made smaller than when glass is used. For example, when glass is used, a thickness of 3 mm is required, whereas when aluminum is used, a thickness of 1 mm is sufficient. As a result, the X-ray transmittance can be improved and the scattering of X-rays by the input window 10 can be reduced, and the performance of the X-ray image tube can be significantly improved.

Furthermore, since the input window 10 made of aluminum can have a convex structure toward the radiation source side, the size of the X-ray image tube can be minimized.

For example, as shown in FIG. 2, if a concave input window 12 (made of titanium, for example) is used, the size of the X-ray image tube will be the same as that of the X-ray image tube when a convex input window 10 is used. The disadvantage is that the dimension A is larger than that of .

However, for example, approximately 2 tons of atmospheric pressure is applied to the input window of an X-ray image tube having an input field of view of 35 cm in diameter.

Furthermore, since the evacuation/heating and degassing process of the X-ray image tube is carried out at approximately 250° C., the strength of the input window is further weakened. For this reason, it is necessary to carefully consider the radius of curvature in the meridian direction and the plate thickness of the manual window.

Now, as shown in Fig. 3, when an external pressure p acts at any point P on the input window, the stress in the meridian direction is 01, the stress in the circumferential direction is σ2, and the plate thickness of the input window is t1.
If the radius of curvature in the meridian direction at point P is rl, and the radius of curvature in the direction perpendicular to the meridian at point P is 2, then σI/ r 1 + a 2 / r 2-1) /
The relationship t holds true. If the radii of curvature of the input windows are all equal, then f and m j 2, so σ-pr2/
2t, but if the radius of curvature is made smaller around the input window, it becomes σt-pr+/2t. Here, considering the relationship rl<r2 in this invention, σ1<σ
Therefore, the stress applied to the input window can be reduced.

However, the radial inflection position (meridian curvature radius position) is
Depending on the type of X-ray image tube, σ1σ2. Since p and * are not constant, it cannot be determined by the law.

The way the radius of curvature changes in the meridian direction is to connect the radius of curvature at the center and the radius of curvature smaller than that in a continuous and differentiable manner at a certain point, as shown by line a in Figure 4. , the radius of curvature is gradually reduced from the center to the periphery, as shown by the lines in the same figure, or the radius of curvature is changed at a constant rate, as shown by the line C in the figure. It's okay.

[Effects of the Invention] As explained above, according to the present invention, the meridional curvature radius of the input window is smaller at the periphery than at the center.
The strength of the manual window is improved, and the required structure can be obtained without making the input window's thickness or radius of meridian curvature unnecessarily thick.

As a result, product reliability and performance can be improved. Furthermore, since it can be manufactured to a minimum size, it can be made smaller and lighter.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing an X-ray image tube according to an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view comparing cases where the input window is convex and concave, and FIG. 3 is a vertical cross-sectional view showing the input window. FIG. 4 is a perspective view illustrating the intensity of curvature in the meridian direction, FIG. FIG. 6 is a longitudinal sectional view showing an X-ray image tube in which the input window has a large radius of curvature in the meridian direction and a small radius of curvature in the meridian direction. Manual window, ... Center of input window, b ... Periphery of input window, ... Vacuum envelope,

Claims (1)

[Claims] In an X-ray image tube equipped with a vacuum envelope in which an input window is hermetically sealed to the open end of a bottomed cylindrical envelope body, the input window has a radius of curvature in the meridian direction. An X-ray image tube characterized in that the area is smaller at the periphery than at the center.