JPH05325853A - X-ray tube - Google Patents

Abstract

PURPOSE:To stably generate X-rays in a small beam diameter and at high intensity without heating a target to high temperatures. CONSTITUTION:An electron flow emitted from an electron gun 12 is projected on the inner peripheral surface of a tubular target 14 and X-rays emitted from the electron-projected portion are repeatedly reflected at the inner peripheral surface of the tubular target 14 and made to go outside of the tubular target 14. The track of projection of the electron flow introduced into the tubular target 14 is controlled by a deflection coil 20 so that the position of projection of the electron flow on the inner peripheral surface of the tubular target 14 is varied throughout the inner peripheral surface, and that the whole inner peripheral surface is employed as the area from which the X-rays emanate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray tube used for a fluorescent X-ray analyzer or the like.

[0002]

2. Description of the Related Art FIG. 4 is a sectional view showing a schematic structure of a Coolidge type X-ray tube which is one of conventional examples of this type of X-ray tube. In the figure, a filament cathode 2 is provided in the tube body 1 of the X-ray tube, and an electron flow a is emitted from the filament cathode 2 which is heated by power supply from a power source (not shown). This electron flow a is focused by the focusing electrode 3.

Further, a filament cathode 2 in the tube body 1
An anode 4 is provided at a position opposite to, and a target 5 is provided between the filament cathode 2 and the anode 4. The electron flow a emitted from the filament cathode 2 toward the anode 4 is projected on the target 5 on the way.
As a result, the target 5 is excited and the target 5 emits X-rays b. The X-rays b are emitted outside the tube through a radiation window 6 provided on the peripheral wall of the tube body 1.

[0004]

However, in the case of the X-ray tube having the above-mentioned structure, since the electron flow a is projected only on a part of the target 5, there is a problem that the intensity of the generated X-ray b is low. .. Further, since the projection of the electron flow a is concentrated on a part of the target 5 and the temperature of the target 5 becomes high, it is necessary to separately provide a cooling mechanism in order to suppress this, and there is also a problem that the configuration becomes complicated.

As an alternative to the Coolidge tube type X-ray tube, there is also known a rotating anticathode type X-ray tube in which the target is rotated so that the projection of the electron flow is not concentrated on a part of the target. In this X-ray tube, although the temperature of the target can be avoided, the point that the electron flow is projected onto only a part of the target is the same as the previous X-ray tube, and therefore, the similar problem of low X-ray intensity is encountered. Have. Further, in the case of this X-ray tube, there is another problem that vibration occurs due to the rotation of the target and the generated X-ray beam becomes unstable.

In view of the above-mentioned conventional drawbacks, the present invention provides an X-ray tube capable of avoiding a high temperature of the target and stably generating an X-ray having a small beam diameter and high intensity. ..

[0007]

In order to achieve the above object, the present invention provides an electron gun which emits an electron stream and a tube-shaped electron stream from which the electron stream is projected on its inner peripheral surface. And a deflection coil which is provided on the outer peripheral side of the target and controls the projection trajectory of the electron flow to change the projection position of the electron flow on the inner peripheral surface of the target.

[0008]

According to the above structure, the X-rays generated on the inner peripheral surface of the tubular target onto which the electron flow is projected are guided while traveling in the direction along the axis of the target while being repeatedly reflected on the inner peripheral surface of the target. Therefore, an X-ray having a small beam diameter is derived from the target. In addition, since the projection trajectory of the electron stream projected from the electron gun onto the inner peripheral surface of the target is changed by the deflection coil, the projection position of the electron stream on the inner peripheral surface of the target is changed, and the projection position is partially changed. It is possible to prevent the temperature of the cathode from rising without concentrating on. Furthermore, since the entire inner circumference of the tubular target can be used as the X-ray generation region, the X-ray intensity is increased accordingly.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a schematic structure of an embodiment of the X-ray tube according to the present invention, and FIG. 2 is an enlarged sectional view showing a part thereof.

An electron gun 12 for radiating an electron flow is supported and fixed by a cylindrical support 13 on one end side of the tube body 11 of the X-ray tube of this embodiment. Also, the electron gun in the tube body 11
The other end facing 12 is made of, for example, copper, molybdenum, etc., and has the same inner diameter (0.5 to 2.0 mmΦ) over the entire length.
A cylindrical tubular target (14) is formed coaxially with the tubular body (11).

The electron gun 12 is a filament cathode 15 which is heated by power supply from a power source (not shown) outside the X-ray tube and emits an electron stream, and a grid which controls the flow rate of the electron stream emitted from the filament cathode 15 to be constant. 16, a focusing unit 17 for focusing the electron flow, and the like.
Further, an alignment coil 18 for aligning the flow of the electron stream emitted from the filament cathode 15 to the focusing portion 17 side is provided on the outer peripheral portion of the tube body 11 corresponding to the installation portion of the electron gun 12.

Between the electron gun 12 and the tubular target 14,
A target joint 19 for introducing the electron flow emitted from the electron gun 12 into the tubular target 14 is arranged. Further, a deflection coil 20 for controlling the projection trajectory of the electron flow introduced into the tubular target 14 is provided on the outer peripheral portion of the tubular body 11 corresponding to the installation portion of the tubular target 14. The deflection coil 20 operates so that the projection position of the electron flow on the inner peripheral surface of the tubular target 14 constantly changes over the entire inner peripheral surface. The tubular body 11 facing the outlet side of the tubular target 14.
A transmission window 21 for transmitting X-rays emitted from the tubular target 14 is provided on the other end side of the.

Next, the operation of the X-ray tube will be described. In the electron gun 12, an electron flow is radiated from the filament cathode 15 heated by power supply from a power source outside the tube (not shown), and the electron flow is aligned by the alignment coil 18 toward the grid 16 side. The flow rate of the electron stream is constantly controlled by the grid 16, and the focusing unit
It is focused and accelerated by 17 and emitted.

The electron flow emitted from the electron gun 12 is introduced into the tubular target 14 from the target joint 19. As shown in FIG. 2, the electron flow a introduced into the tubular target 14 is projected on the inner peripheral surface of the tubular target 14, the projecting portion thereof is excited, and X-rays b are radiated therefrom.

The radiated X-ray b advances toward the exit side where the transmission window 21 is arranged while repeating reflection on the inner peripheral surface of the tubular target 14. By this operation, the X-ray b is focused along the axis of the tubular target 14. Therefore, the beam diameter of the X-ray b emitted from the tubular target 14 becomes thin according to the tubular diameter of the tubular target 14.

Further, the projection locus of the electron flow a introduced into the tubular target 14 is such that the projection position of the electron flow a on the inner peripheral surface of the tubular target 14 always changes over the entire inner peripheral surface. Can always be changed by X
The line b is emitted from the entire inner peripheral surface of the tubular target 14, and the intensity of the X-ray b emitted from the tubular target 14 is correspondingly increased.

Furthermore, since the projection position of the electron flow a on the inner peripheral surface of the tubular target 14 constantly changes, it is possible to avoid the situation where the projection of the electron flow a is concentrated on a part and the temperature of the tubular target 14 becomes high. It will also be done.

In the embodiment shown in FIGS. 1 and 2,
Although the tubular target 14 is a monotonous cylindrical tube having a constant tube diameter over the entire length, the present invention is not limited to this, and as shown in FIG.
Various shapes can be selected as shown in (d). That is, the tubular target 14 shown in FIG.
Is a spheroidal shape in which the diameters of the inlet 14a and the outlet 14b are reduced and the diameter of the middle body is increased, and FIG. 3 (b) shows the direction from the inlet 14a to the outlet 14b. The pipe diameter is gradually increased to form a taper shape.
On the contrary, (c) shows a taper shape in which the pipe diameter gradually decreases from the inlet 14a to the outlet 14b, and in FIG. 3 (d), the pipe diameter from the inlet 14a to the middle is gradually increased. It has a parabolic shape and thereafter has a constant pipe diameter up to the outlet 14b. By properly using these tube-shaped targets 14, it is possible to obtain X-rays having a focusing degree and intensity according to the application.

[0019]

According to the present invention, which has the above-described structure, the electron stream emitted from the electron gun is projected onto the inner peripheral surface of the tubular target, and X-rays generated there are repeatedly reflected on the inner peripheral surface of the target. In addition to guiding in the direction along the axis of the, the projection trajectory of the electron flow projected from the electron gun into the target is changed by the deflection coil, so that the temperature of the cathode can be prevented from rising and the beam diameter can be made small and strong. It is possible to stably generate high X-rays.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a schematic configuration of an X-ray tube according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a trajectory of an electron flow and an X-ray in a tubular target in the X-ray tube of the above embodiment.

FIG. 3 is a cross-sectional view showing various modifications of the tubular target.

FIG. 4 is a sectional view showing an example of a conventional X-ray tube.

[Explanation of symbols]

 12 ... Electron gun, 14 ... Tube target, 20 ... Deflection coil.

Claims (1)

[Claims] 1. An electron gun for radiating an electron stream, a target having a tubular shape on which an electron stream from the electron gun is projected, and a projection trajectory of the electron stream provided on the outer peripheral side of the target. An X-ray tube comprising: a deflection coil that controls and changes the projection position of the electron flow on the inner peripheral surface of the target.