JPS6047331A - Impregnated type cathode - Google Patents

Abstract

PURPOSE:To offset the insufficient impregnation of electron emission material near the central part of a cathode substrate by forming a hollow cylinder that is integratedly comprised with the cathode substrate, on the rear of the cathode cylinder and coating only the rear surface of the cathode substrate corresponding to the external section of this hollow cylinder then performing brazing and sealing hole treatment. CONSTITUTION:Brazing material 4 is applied to only the external section of a hollow cylindrical body 4 that is integratedly comprised with a cathode substrate 1 on the rear of the cathode substrate 1. Since such structure does not require the sealing hole treatment near the central part in which the thickness of the cathode substrate 1 is smallest, the insufficient impregnation of electron emission material can be offset due to the intrusion of brazing material and a cathode with more homogeneous electron emission characteristics can be obtained. In addition, since a heater coil is connected to the inner part of a sleeve 2 and the hollow cylindrical body 5, thermal conduction efficiency is improved.

Description

[Detailed description of the invention] The present invention relates to impregnated wall cathodes.

The impregnated cathode is used as the cathode of major electron tubes such as traveling wave tubes, klystrons, and CRTs because it has a high current density, such as C, and has a long life.

FIG. 1 is a schematic sectional view for explaining the entire structure of such an impregnated cathode. A porous cathode substrate 1 formed by sintering tungsten powder is brazed to a cylindrical cathode sleeve 2 made of a heat-resistant metal such as molybdenum using a brazing material 4tl. Further, the back surface of the cathode substrate 1 is sealed using four fillers of brazing material. On the other hand, barium oxide 1 is present in the pores of the cathode substrate 1.
It is impregnated with an electron emitting material (not shown) made of calcium oxide, aluminum oxide, etc. The cathode substrate 1 is heated to a predetermined temperature by the heater 3, and all electrons are emitted from the surface.

In the impregnated cathode having such a configuration, the reason why the back surface of the cathode substrate 1 is completely sealed is to prevent the above-mentioned electron emitting substance from evaporating and adhering to the heater coil.

Now, such brazing and sealing treatment is usually performed using Mo5
A powder of 0 wt % - 40 wt % Ru, mixed with a suitable binder, such as a mixed lacquer of nitrified cotton and amyl acetate, is applied to the back side of the cathode substrate 1 (7. ~2100℃
This is done by heating. However, the cathode substrate 1 usually has 18 to 20 continuous pores. Due to its porous nature, when the brazing filler metal is melted, a considerable amount is absorbed into the cathode substrate, creating an inconvenience that a void is created between the cathode substrate 1 and the sleeve 2.

On the other hand, if too much brazing material is applied, there is an inconvenience that the brazing material may penetrate deep into the cathode substrate 1 or may flow to the surface of the cathode, that is, to the 1 gL radiation resistance c. In particular, as shown in FIG. 1, when the cathode surface is concave, there is a risk that the amount of electron emitting material impregnated near the center may be reduced.

The present invention has been made in order to overcome the above-mentioned disadvantages, and a hollow cylinder integrally formed with the cathode substrate is entirely formed on the back surface of the cathode substrate, and only on the back surface of the cathode substrate corresponding to the outside of the hollow cylinder. It is characterized by applying brazing filler metal to perform brazing and sealing.

The purpose of this is to completely eliminate the infiltration of the brazing filler metal into the vicinity of the central part of the cathode substrate, thereby completely eliminating the lack of impregnation of the electron emitting material in the vicinity of the central part.

Examples will be described below with reference to the drawings.

FIG. 2 is a sectional view of essential parts of the impregnated cathode according to the present invention. 1 to 4 in the same figure are the same as those in FIG. 1, so the same numbers are used and a complete explanation will be omitted. FIG. 2 shows a hollow cylindrical body integrally constructed with a 5-digit cathode substrate 1, and the brazing material 4 is connected to the cathode substrate l.
It is applied only to the outer side of the hollow cylindrical body 5 on the back side of the hollow cylinder 5.

This structure eliminates the need for sealing near the center of the cathode substrate 1, where the wall thickness is the smallest, which makes it possible to completely eliminate insufficient impregnation of the electron emitting material due to infiltration of the brazing filler metal, and to achieve more uniform electron emission. A cathode with radiation properties could be provided.

Furthermore, as another effect of the present invention, since the He-Goo coil is inserted inside the sleeve 2 and the hollow cylindrical body 5, the heat conduction efficiency is improved compared to the conventional structure.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional impregnated cathode, and FIG. 2 is a sectional view of an impregnated cathode according to the present invention. ]... Cathode base, 2... Cathode sleeve, 3... Heater, 4... Brazing material, 5... Hollow cylindrical body. Figure 1-2

Claims (1)

[Claims] In an impregnated cathode of an indirectly heated type having a porous tungsten base and a cylindrical cathode sleeve made of a heat-resistant metal, a hollow cylindrical body integrally formed with the porous tungsten base is formed on the back surface of the porous tungsten base. An impregnated cathode characterized in that only the back surface of the porous tungsten substrate in the portion surrounded by the hollow cylinder and the cathode sleeve is sealed.