JPS60101848A - X-ray tube - Google Patents

Abstract

PURPOSE:To obtain large X-ray output with the use of a glass envelope, by attaching a shield plate made of a heat-resistant insulation material to a cathode so as to shield the focusing electrode of the cathode and the target of an anode from the glass envelope. CONSTITUTION:A shield plate 7 is attached and fixed to a cathode 2a. The shield plate 7 is made of a heat-resistant insulation material such as quartz or porcelain, and disposed between a glass envelope 1 and a focusing electrode 3, target 5 and so on. The size of the shield plate 7 is determined so that the plate covers at least a region of the inner surface of the glass envelope 1 on which electrons dispersed from the focus 6 can impinge. When the X-ray absorption of the shield plate 7 is large, a transmittable hole 8 is provided at least in the area where the X-ray cone passes through. In such a manner, the heat radiated from the target and the electrons dispersed from the focus during generation of X-rays do not enter directly into the envelope but penetrate in the shield plate. Consequently, even if the X-ray output is increased, the gas is effectively prevented from being emitted from the envelope.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an X-ray tube having a structure particularly suitable for generating a large X-ray output.

[Background of the invention]

In a conventional X-ray tube, as shown in FIG. 1, a cathode 2 is attached to one end of a glass envelope 1, and thermionic electrons emitted from a focusing electrode 3 at the tip of the cathode 2 are transferred between the cathode 2 and anode 4. It is accelerated at high speed by a high voltage applied therebetween, and collides with a focal point 6 of a target 5 provided on an anode 4 facing a focusing electrode 3 to generate X-rays. In the case of a normal X-ray tube, when generating X-rays, only a portion (approximately 1%) of the energy given to the target by the electron beam is converted into X-rays, and most of the rest becomes heat and hits the target. Red hot, about 1/3 of it
The electrons become scattered electrons and are scattered in areas other than the focal point 6.

Therefore, the glass envelope 1 receives thermal radiation due to the red heat of the target 6 and scattered electrons. When increasing the X-ray output, the amount of thermionic electrons emitted toward the focal point also increases, so the collision of thermal radiation from the target and scattered electrons with the glass envelope 1 increases, which causes the gas contained in the glass to There was a problem in that the vacuum level inside the X-ray tube was lowered. For this reason, the increase in output of the X-ray tube has been limited by the glass envelope.

As a means of eliminating such limitations and obtaining large X-ray output, there is a method in which part of the envelope that receives thermal radiation and scattered electrons is made of metal, but in that case, the structure of the envelope is Not only is it complicated and expensive, but it also has the drawback that it cannot withstand the high voltage applied between the cathode and anode, and the voltage that can be applied is limited.It also makes it impossible to see inside the X-ray tube. X
There is also the problem that it is inconvenient when manufacturing or using the wire tube.

(Object of the Invention) The object of the present invention is to use the xIJ! which uses a glass envelope and can obtain a large X-ray output! ! The purpose is to provide tubes.

[Summary of the invention]

In order to achieve the above object, in the present invention, a shielding plate made of a heat-resistant insulating material is attached to the cathode, and this shielding plate shields the focusing electrode of the cathode and the target of the anode from the glass envelope. I made it.

[Embodiments of the invention]

FIG. 2 is a diagram showing an embodiment of the present invention. glass envelope 1,
The anode 4 is similar to the conventional X-ray tube shown in Figure 1, but
A shielding plate 7 is fixedly attached to the cathode 2a. The shielding plate 7 is made of a heat-resistant insulating material such as quartz or porcelain, and is disposed between the focusing electrode 3, target 5, etc. and the glass envelope 1 to prevent electrons scattered from the focal point 6 from colliding with each other. The shielding plate 7 has a size that covers the inner surface of the glass envelope 1 that may be exposed to the inner surface of the glass envelope 1.The shielding plate 7 may be placed in contact with the inner surface of the glass envelope 1, or may be spaced apart so as not to contact the inner surface of the glass envelope 1. If the X-ray absorption of the shielding plate 7 is large, a through hole 8 is provided at least in the range through which the X-ray beam cone passes.
The figure shows the shielding plate 7 viewed from the X-ray emission direction, and FIG. 4 is a top view of the shielding plate 7.

With the above configuration, thermal radiation from the target and scattered electrons from the focus when X-rays are generated enter the shielding plate and do not directly enter the glass of the envelope, so even if the X-ray output increases. There is no risk of gas being released from the glass envelope. The shielding plate does not require functions such as vacuum sealing that are required for the envelope, and materials with better heat resistance than glass can be used exclusively for the parts that require heat resistance. It is possible to use materials that have a high resistance to gas release due to thermal radiation and scattered electrons.

Furthermore, since the shielding plate is made of an insulating material, there is no risk of disturbing the trajectory of the electron beam from the focusing electrode toward the focal point, and there is no risk of impairing the maintenance of the high voltage applied between the cathode and the anode.

〔Effect of the invention〕

As explained above, according to the present invention, there is no risk of gas being released from the glass of the envelope when X-rays are generated, and there is no risk of damaging the withstand voltage characteristics of the X-ray tube. It is possible to manufacture an X1m tube with a glass envelope that provides linear output.

[Brief explanation of drawings]

Fig. 1 is a front view of a conventional X-ray tube, Fig. 2 is a front view of an embodiment of the present invention, Fig. 3 is a view of the shielding plate seen from the X-ray emission direction, and Fig. 4 is the shielding plate. FIG. 1 is a top view of 1.-Glass envelope, 2.-Cathode, and Focusing electrode.
4-・Anode, 5-Target, 6-・Focal box 1 Figure 3 Figure Z Figure 4

Claims (1)

[Claims] In an X-ray tube equipped with a cathode and an anode in a glass envelope, a shielding plate made of a heat-resistant insulating material is attached to the cathode, and this shielding plate connects the focusing electrode of the cathode and the target of the anode to the glass envelope. An X-ray tube characterized in that it is shielded from light.