JPS62222553A - X-ray image tube device - Google Patents

Abstract

PURPOSE:To improve the structure of a magnetic shield wall, and realize a source saving and a lightweight, by forming a magnetic shield mainly of a highly permeable powder agent directly at the outside of a vacuum envelope. CONSTITUTION:At the necessary portions of a glass vacuum envelope 25, a mixture of a high permeability powder agent and a binder is spread and dried. It is spread and formed into a membrane 1 at a necessary thickness at the portions of the envelope to get a magnetic shield function. For this purpose, it is spread thicker at the input side and thinner at the output side. By applying a metallic powder such as a permalloy in such a way, it acts as a conductive membrane, as well as it is effective to reject the charge at the vacuum envelope. Therefore, the magnetic shield wall of a high permeability can be minimized irreducibly and formed with a small amount of source while the handling is made easy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an X-ray image tube device, and particularly to the structure of its magnetic shield.

(Prior Art) Generally, an X-ray image tube is an electron tube that converts radiation such as X-rays and R-rays into visible images. This X-ray image tube is equipped with an input phosphor screen that converts an X-ray image into a visible image at one end of the vacuum envelope, and a photocathode that emits photoelectrons depending on the strength of the light in the visible image. and a focusing electrode and an anode for accelerating and focusing the photoelectrons, and an output phosphor screen that emits light from the accelerated and focused photoelectrons and displays a visible image thereon at the other end of the real envelope. It has become.

When actually using an X-ray image tube, the earth's magnetic field bends the electron trajectory, distorting the image that appears on the output phosphor screen. To prevent this, a magnetic shield is placed outside the vacuum envelope of the image tube. The walls were designed to avoid being affected by the earth's magnetic field. As an example of this, an X-ray image tube device having a structure as shown in FIG. 3 has been put into practical use.

That is, this X-ray image tube device is composed of an X-ray image tube (a) and a cylindrical casing (38) that houses this tube. The X-ray image tube (branch) has an input sensor at one end.
The ampulla formed at this ampulla (221) and the shoulder (23
), and the other end is closed.
It has a glass vacuum envelope (25) consisting of (24).

The vacuum envelope (25) is provided with an input surface (26) consisting of an input fluorescent screen and a photocathode (not shown) on the inside adjacent to the input window (21). (
A focusing electrode (27) is arranged on the inner wall of 25).

On the other hand, a cylindrical anode (28) is provided at the end of the small diameter cylindrical portion (24) made of glass, and an output fluorescent screen (29) is provided surrounded by this anode (28). It is being

Further, a holding structure (30) is attached to the outer wall surface of the shoulder (23) of the vacuum envelope (25) of such an X-ray image tube (a).
are arranged coaxially.

The X-ray image tube having such a configuration is housed in a cylindrical housing (38) in which an X-ray shield wall (36) and a magnetic shield wall (37) are sequentially formed on the inner wall, and an output phosphor screen (29).
) side through the tube holding plate (34) and screw (3).
1) is fixed to the cylindrical casing (38).

By the way, as shown in Fig. 4, the magnetic shielding wall (37) is made by rolling a plate material such as permalloy into a cylindrical shape and spot welding the joined parts at a plurality of resistance welding points (40) to obtain magnetic properties. After the heat treatment, it is fixed in a cylindrical casing (38).

As a result, the magnetic shield wall (37) has a function of preventing the influence of earth's magnetism on the tube electrodes.

In addition, an alkali metal is vapor-deposited during the manufacturing process to form the input surface (26) of the X-ray image tube, but this alkali metal also adheres to the insulator inside the tube, and when light hits this part, photoelectrons are generated. It emits and appears as noise on the output screen. To prevent this, a black paint is applied to the outer surface of the glass vacuum envelope, and a conductive film of carbon powder is formed on the outer surface to prevent electric discharge caused by the electric charge on the glass surface. is being eased.

(Problems to be solved by the invention) Focusing electrode (27) of X-ray image tube, cylindrical anode (28)
The applied voltage becomes higher from the input surface (26) to the output surface (29), and becomes less susceptible to the influence of earth's magnetism, which acts to bend the electron trajectory. Therefore, regarding the function of the magnetic shield wall (37), the magnetic field attenuation rate may be lower on the output side than on the input side. That is, the thickness of the magnetic shielding wall (37) may be gradually reduced from the input surface to the output surface, but a material with a uniform thickness is used for ease of machining, which is not preferable in terms of resource utilization. In addition, in an X-ray image tube having a structure in which a metal member made of ferromagnetic material is used as a part of the vacuum envelope (25) of the X-ray image tube, the magnetic shielding effect of the metal member may be sufficient. In this case, the function overlaps with that of the magnetic shield wall (37), which is also not preferable in terms of resource utilization. Furthermore, the conventional structure of the X-ray image tube has the disadvantage that it is difficult to reduce the weight.

The purpose of this invention is to improve the structure of the magnetic shield wall in an X-ray image tube device, thereby saving resources and reducing weight.

(Structure of the Invention) (Means for Solving the Problems) This invention does not use a plate material for the magnetic shield wall, but forms a magnetic shield whose main component is a high magnetic permeability powder directly on the outside of the vacuum envelope. This constitutes an X-ray image tube that is not affected by the earth's magnetic field.

(Function) To provide an X-ray image tube that shields earth's magnetism with a magnetic shield mainly composed of high magnetic permeability powder and obtains a desired electron trajectory, making it light and capable of obtaining distortion-free images. I can do it.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Note that, like the conventional example, the same parts are given the same reference numerals.

The embodiment shown in FIG. 1 is an example in which a mixture of a high magnetic permeability powder and a binder is coated and dried on the required portions of a glass vacuum envelope (25). This is made by applying a coating film to each part of the envelope to the required thickness for magnetic shielding function. Therefore, the input surface side is thick and the output surface side is thinner. For example, when permalloy is used as a high permeability powder, the powder thickness on the input surface side is 0.
．． 7#, and the output surface side is 0.2#, and the powder thickness between them may be between them.

Incidentally, since the high magnetic permeability powder of this example does not have binding strength by itself, a binder is used to apply it.

The X-ray image tube device of this embodiment uses a metal powder such as permalloy as the high magnetic permeability powder, so that it also serves as a conductive film and has the effect that the vacuum envelope is not charged with electric charge. Furthermore, by using ferrite powder as the high magnetic permeability powder, the ferrite powder exhibits a black color and can therefore also serve as a light shielding film.

Next, a main part of another embodiment of the present invention is shown in FIG.

That is, FIG. 2 shows a cross section of a vacuum envelope of an X-ray image tube, and is an example in which a ferromagnetic material such as an iron-nickel alloy is used for a part of the envelope (25). In this case, by forming the high magnetic permeability powder only in the portion excluding the ferromagnetic member, the same effect as in the above embodiment can be achieved.

(Effects of the Invention) As described above, according to the present invention, the magnetic shielding wall with high magnetic permeability can be minimized, and a lightweight X-ray image tube device that is easy to handle and uses few resources can be provided. .

Furthermore, by selecting a powder material with high magnetic permeability, it also has the effect of serving as a conductive film and a light-shielding film.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part showing one embodiment of the present invention, FIG. 2 is a sectional view of a main part showing another embodiment of the invention, and FIG. 3 is a sectional view of a conventional X-ray image tube device. , FIG. 4 is a perspective view showing a main part of FIG. 3. 1...Magnetic shield wall Translation...X-ray image tube 3
8...Cylindrical casing 25...Vacuum envelope Agent Patent attorney Norio Chika Ken Yudo Ogo Norio Figure 1 Figure 2 Figure 3 Figure 4

Claims (3)

[Claims] (1) In an X-ray image tube device equipped with an X-ray image tube and a casing that houses the X-ray image tube, the outer wall of the vacuum envelope of the X-ray image tube is coated with a high magnetic permeability powder as a main component. An X-ray image tube device characterized in that it is formed by directly forming a magnetic shield. (2) X according to claim 1, wherein the high magnetic permeability powder is permalloy or ferrite powder.
Line image tube device. (3) The X-ray image tube device according to claim 1, characterized in that a coating film of a mixture of a high magnetic permeability powder and a binder is formed on a vacuum envelope.