JPS58214255A - X-ray tube for rotary anode - Google Patents

Abstract

PURPOSE:To make the x-ray tube for a rotary anode that has a large capacity to obtain a number of x-rays, compact and capable of resisting to high voltage without increasing the shape of a glass bulb by uniformalizing and reducing the influence of the radiant heat and scattering electrons from an anode target on the glass bulb when the x-rays are generated. CONSTITUTION:The electron flow emitted from the filament (not illustrated) in a focusing electrode 4 is focused and collides with the focal point 10 of an anode target 5 and then generates x-rays. In this case, since the anode target 5 is revolved, the heat generated in the focal point 10 of the anode target 5 is scattered in the whole circumferential direction of the anode target 5 and is not scattered in a specific direction. Besides, since the length between the anode target 5 and an x-ray radiation window section 8 is expanded by providing a glass bulb protrusion 9 at least within the range of a cone of the x-ray radiation window section 8 of a glass tube 1 formed by applicable x-ray beams, the density of the scattering electrons colliding with the inner wall surface of the x-ray radiation window section 8 is reduced and the incident density of the radiant heat can also be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotating anode X-ray tube, and particularly to an improvement in the structure of a vacuum envelope.

In general, a rotating anode X-ray tube has a cathode body placed at one end of the vacuum envelope and a rotating anode body placed at the other end. There is a need for a function to maintain the temperature, withstand the high voltage applied to the anode body when generating X-rays, and transmit the generated X-rays in a usable state to the outside. In order to fulfill this function, glass pulp has been widely used as a vacuum envelope for X-rings.

FIG. 1 is a sectional view of a main part showing an example of a conventionally used rotating anode X-ray tube. In the figure, a cathode body 2 is disposed at one end of the glass pulp 1, and a rotating anode body 3 is disposed at the other end. This cathode body 2 has a focusing electrode 4 and a filament (
(not shown). The rotating anode body 3 includes an umbrella-shaped anode target 5 and a rotor 6 that supports the anode target 5 and is rotatable together with a rotating shaft (not shown).
The rotating shaft is supported via a ball bearing, and the bearing box 7 has an end extending outward from the glass pulp 1. The glass bulb 1 is made of heat-resistant glass such as silicate glass, and its center portion is formed to have a large diameter corresponding to the outer diameter of the anode target 5, and the cathode body 2 and rotating The portion on the anode body 3 side is also formed to have a smaller diameter than the central portion, and each of these portions is formed into a concentric cylindrical shape.

In the rotating anode X-ray tube configured in this manner, X-rays are generated by a high voltage applied between the cathode body 2 and the anode body 3, which generates an electron current emitted from a filament (not shown) in the collecting electrode 4. It is accelerated and collides with the anode target 5, causing
A ray is generated, passes through the X-ray emission window 8 of the glass bulb 1, and is emitted within the range in the direction of the arrow AA'. In this case, among the electron streams emitted from the filament and colliding with the anode target 5, the energy of the electron stream that is not converted into X-rays becomes heat and makes the anode target 5 red-hot, and a part of it becomes scattered electrons. After being scattered, it flows back into the anode target 5, and a part of it also flows into the X of the glass bulb 1.
The radiation collides with the inner wall surface of the radiation window section 8. Therefore, the longer the X-ray generation continues, the more the area near the X-ray radiation window 8 of the glass bulb 1 is repeatedly exposed to thermal radiation and scattered electrons from the red-hot anode target 5. As a result, the glass bulb 1 could not withstand the usage conditions even in response to the demand for manufacturing a large-capacity X-ray tube to obtain a large amount of X-rays, and the normal operation of the X-ray tube due to gas released from the glass bulb. The problem arises that movement is hindered.

As a solution to this problem, a large-capacity type X
An X-ray tube that uses metal instead of glass near the center of the vacuum envelope has been proposed as a ray tube, but in such a configuration, the X-ray tube envelope does not have the ability to maintain high voltage. There were problems such as the structure for transmitting X-rays to the outside of the envelope became complicated.

Therefore, the present invention has been made in view of the above-mentioned drawbacks of the conventional technology, and its purpose is to provide a large-capacity type that is compact, has excellent high voltage resistance characteristics, and can be manufactured with a relatively simple structure. An object of the present invention is to provide a rotating anode X-ray tube.

In order to achieve such an object, the present invention is such that only the X-ray emission window of the glass bulb is formed to protrude in the radial direction of the bulb. In other words, the heat emitted from the @polar target during X-ray generation passes through the glass and is dissipated to the outside of the X-ray tube, but some of it is absorbed into the glass and increases its temperature. Scattered electrons from the anode target are superimposed on top of the anode target, causing a temperature rise and outgassing due to electron impact. For this reason, it must be used within a limit that does not cause outgassing from the glass. On the other hand, in order to obtain a large amount of X-rays, a large amount of electron flow is poured into the anode target, which increases heat dissipation and scattered electrons. and,
In order to satisfy these contradictory conditions, the present invention reduces the amount of radiant heat and scattered electrons received per unit area of the glass bulb by increasing the distance between the positive target and the glass bulb. Moreover, simply increasing the distance would result in a large glass bulb, so we focused on the fact that the density of scattered electrons from the anode target is high in the XH emission window direction, and set the anode only in the X-ray emission window direction. This uses a specially shaped glass bulb with a long distance between the target and the glass bulb.

Embodiments of the present invention will be described in detail below using the drawings.

FIGS. 2 and 3 are cross-sectional configuration diagrams of essential parts showing an example of a rotating anode X-ray tube according to the present invention. 2 is a longitudinal sectional view, and FIG. 3 is a sectional view taken along the line 2--2 in FIG. 2. Since the same symbols as in FIG. 1 represent the same elements, their explanations will be omitted. In these figures, the glass bulb 1 has at least an X-ray cone (
A glass bulb protrusion 9 in which an X-ray emission window 8 including a conical shape surrounded by an xg emission range A-A protrudes a glass bulb wall in a direction perpendicular to the tube axis of the X-ray tube.
are integrally formed. In other words, in order to prevent the central axes of the cathode body 2 and the rotating anode body 3 from being eccentric, only the X-ray emission window 8 of the glass bulb 1 is provided with the protruding portion 9 that protrudes in a direction perpendicular to the tube axis. Only this X-ray emission window section 8 is configured such that the distance in the direction perpendicular to the tube axis is longer than in the other directions.

In the rotating anode X-ray tube configured in this way, the electron flow emitted from the filament (not shown) in the focusing electrode 4 is focused and impinges on the focal point 10 of the anode target 5, generating X-rays. . In this case, since the ridge target 5 rotates, the heat generated at the focal point 10 of the anode target 5 is dissipated in the entire circumferential direction of the anode target 5, and is not dissipated in a concentrated manner in a specific direction. However, focus 1
0 is located in a specific direction eccentric from the center axis of the X-ray tube determined by the placement position of the focusing electrode 4. In the direction of the electrode 4, scattered electrons do not flow back into the anode target 5, and more of them collide with the glass bulb 1. Here, if we look at the scattered electrons colliding with the glass bulb 1 in the tube axis direction of the X-ray tube, we can see that the anode target 5
On the opposite side of the inclined surface facing the cathode body 2, the electric field is blocked by the anode target 5 itself, and the electric field decreases, and on the cathode body 2 side, the electric field is blocked by the electric field. That is, in the range of the so-called X-ray beam cone that surrounds the inclination angle of the anode target 5 from the focal point 10 to the direction perpendicular to the central axis of the X-ray tube, the number of scattered electrons toward the glass bulb 1 increases. By providing the glass bulb protrusion 9 at least in the range of the Xi utilization beam of the X-ray emission window 8 of the bulb 1, the anode target 5 and the X-ray emission window 8
Since the distance between the X-ray radiation window 8 and the X-ray emission window 8 is increased, the degree of scattering electrons impinging on the inner wall surface of the X-ray emission window section 8 can be reduced, and the incident density of radiant heat can also be reduced.

As explained above, according to the present invention, in a rotating anode X-ray tube in which a cathode body and a rotating anode body are disposed on the same axis within a glass bulb, the anode target from the anode target to the glass bulb when X-rays are generated. Since the effects of radiant heat and scattered electrons are averaged and reduced, it is possible to downsize a large-capacity rotating anode X-ray tube that can obtain a large amount of X-rays without increasing the size of the glass bulb. It has various excellent effects, such as being able to withstand high voltage, being able to manufacture it with a relatively simple structure, and being inexpensive and low-profile.

[Brief explanation of the drawing]

FIG. 1 is a sectional configuration diagram of main parts showing an example of a conventional rotating anode X-ray tube, and FIGS. 2 and 3 are main parts corresponding to FIG. 1 showing an example of a rotating anode X-ray tube according to the present invention. They are a partial sectional view and a sectional view taken along ■-■. 1...Glass bulb, 2.e...Cathode body, 3...
・Rotating anode body, 4...Focusing electrode, 5...Anode target, 6...Rotor, 7...Bearing box, 8...
...X-ray emission window part, 9...glass bulb protrusion part,
10...Focus. Figure 1

Claims (1)

[Claims] In a rotating anode X-ray tube in which a cathode body and a rotating anode body are arranged facing each other on the same tube axis within a glass bulb, at least the range of the X-ray utilization cone of the glass bulb is directed in a direction orthogonal to the tube axis. 1. A rotary anode X-ray tube, characterized in that a bulb protruding portion is provided, and the distance between the target of the rotary anode body and the glass pulp is longer than in other directions.