JPS6215732A - Manufacture of electron gun structure for microwave tube - Google Patents

Abstract

PURPOSE:To manufacture an electron gun assembly from which stable electrons can be taken out, by placing a positioning jig in contact with the end of a cathode sleeve to perform assembly work. CONSTITUTION:A flange 22a is provided at the end of a cathode sleeve 22, which is coupled to an impregnated cathode base 21. The cylindrical portion 30 of a jig 29, which is used for positioning when a Wehnelt cylinder 28 is secured to an outer support cylinder 27 for the sleeve 22, is placed in contact with the flange 22a. The jig 29 is thus used to keep the distance between the end face of the WEhnelt cylinder 28 and the surface of the base 21 accurate and manufacture a cathode structure 20 without touching the surface of the base 21, which is prohibited to be touched during assembly work because a thin film is provided on the surface. This results in providing an electron gun capable of emitting stable electrons.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an electron gun assembly for a microwave tube suitable for use in traveling wave tubes and klystrons mounted on satellites that particularly require high reliability. Regarding the manufacturing method.

[Technical background of the invention]

Generally, high-power traveling wave tubes for use in satellites require high current density, and impregnated cathodes are used as suitable cathodes. The main characteristics required for this impregnated cathode for use on a satellite are listed below.

(1) Long life.

For example, it should have a long life of 60,000 hours or more.

(2) Operate with low power consumption.

The only power source for the satellite is the energy supplied from the solar cells onboard the satellite.

It is very important to have low power consumption.

(3) Must be able to withstand shocks such as during satellite launches.

(a) No deformation due to impact during launch.

(b) If the heater embedding agent falls off, the heat from the heater will not be effectively transferred to the cathode.

The cathode temperature decreases, causing deterioration of characteristics.

(c) If the heater embedding agent falls off, it becomes a foreign object inside the tube and interferes with the characteristics of the electron tube or causes discharge inside the tube.

By the way, the electron gun assembly conventionally used in microwave tubes consists of a cathode assembly and a Wehnelt electrode, and the cathode assembly 13 is shown in (&) in FIG.

(b) shows the manufacturing method of the electron gun assembly. First of all,
To explain the cathode structure 13, 1 in the figure is an impregnated cathode substrate, in which tungsten powder with a particle size of about 3 μm is mixed with a specific gravity of 1.
BaO1CaO is sintered to a porous tungsten base of about 6.

It was obtained by impregnating it with an electron-emitting substance such as At203. 2 is a cathode sleeve made of a high melting point metal such as molybdenum. One end of this cathode sleeve 2 and the cathode base 1 are joined with an alloy brazing material 3 of molybdenum and ruthenium.

4 so that the cathode substrate 1 reaches the desired operating temperature.

This is a heater for heating. 5 is an embedding agent for embedding the heater 4 in the cathode sleeve 2. In this case, alumina powder is turned into a slurry with an organic binder and filled into the cathode sleeve 2, and then heated and sintered at high temperature in hydrogen or vacuum to be fixed inside the cathode sleeve 2. .

Such an impregnated cathode has a higher operating temperature of 980 to 1050°C than a conventional oxide cathode, which increases the heater temperature and causes the heater 4 to break.
By embedding the heater 4 in the embedding agent 5 as described above, the operating temperature of the heater 4 can be lowered, so the embedding agent 5 plays an extremely important role in the impregnated cathode.

The cathode sleeve 2 is fixed to the outer support cylinder 7 via a plurality of supports 6 to form a cathode assembly 13.

By connecting a Wehnelt electrode to such a cathode assembly 13, an electron gun assembly is completed.Next, a method for manufacturing the same will be explained with reference to FIG. 2(a).

In general, the structure of an electron gun for a microwave tube requires high perveance, extracts the necessary current from a cathode with a large area, and focuses this electron current into a beam with a small cross section. An electron beam with an extremely high density compared to the emission current density of the cathode can be obtained.

The structure of such an electron gun structure is called a Pierce-type electron gun, and the Wehnelt electrode 8 shown in FIG. 2(b) plays one of the roles of forming an electron beam. This has the same electrical potential as the cathode structure, that is, the impregnated cathode,
It is assembled using jigs 9 and 12. In order to obtain the designed electron beam, the distance between the impregnated cathode substrate 1 and the tip of the Wehnelt electrode 8 must be set with high precision. The distance to the center has been taken into account to ensure accurate appearance. Further, a cylindrical body 11 is attached to the jig 9 so that the cathode structure 13 is grounded at the center of the Wehnelt electrode 8. Then, the Wehnelt electrode 8 is inserted into the jig 9, and then the cathode assembly 13 is inserted therein and arranged in the designed manner, and then the lower end of the outer support cylinder 7 of the cathode assembly 13 is inserted. and the lower end of the Wehnelt electrode 8 are resistance welded together.

[Problems with background technology]

However, the above-mentioned conventional method for manufacturing an electron gun assembly has the following drawbacks. That is, the surface of the impregnated cathode substrate 1 is easily scratched. in general.

The impregnated cathode has the disadvantage of high operating temperature, but in order to improve this point, after impregnating the electron emitting substance, the surface of the impregnated cathode substrate 1 is coated with Os, In, etc. by vapor deposition or sputtering. A method is used to lower the work function of an impregnated cathode by attaching a thin film to lower its operating temperature. Since this thin film is as thin as 100 OX to several thousand stripes, it is easily damaged and is a process that requires special care in the manufacturing method of the electron gun assembly. Do not touch surfaces.

However, as in the assembly method shown in FIG. 2(b), the spherical part 10 provided in a part of the jig 9 is pressed against the center of the cathode base 1 to obtain the dimensions with respect to the Wehnelt electrode 8. At this time, in order to obtain accurate dimensions, a certain amount of force is applied to press the cathode substrate 1, so that the center portion of the cathode substrate 1 where the tip of the spherical portion 10 is in contact is slightly scratched. When this part was viewed under a microscope, it was confirmed that the thin film layer was deformed.

By scratching a part of the surface of the cathode substrate 10 in this way, electron emission from the surface of the cathode substrate 1 is disturbed,
It becomes impossible to extract uniform electrons. Also, jig 9
Pressing on the impregnated cathode substrate 1 will not contaminate the surface of the impregnated cathode substrate 1, which is undesirable due to the characteristics of the impregnated cathode.

[Purpose of the invention]

An object of the present invention is to provide a method for manufacturing an electron gun assembly for a microwave tube that can stably extract good electrons by improving the cathode sleeve.

[Summary of the invention]

In this invention, an impregnated cathode substrate is fixed to one end of a cathode sleeve that houses a heater inside and is fixed with a heater embedding agent, and further, the cathode sleeve is fixed to an outer support cylinder via a support, and the outer side of the cathode sleeve is In the method for manufacturing an electron gun assembly for a microwave tube, the electron gun assembly is provided with a Wehnelt electrode coaxially on the outside of a supporting cylinder and the impregnated cathode substrate, including: an end portion of the cathode sleeve that is joined to the impregnated cathode substrate; A flange expanding outward is integrally formed in the flange, and the cylindrical part of the jig for alignment with the Wehnelt electrode is applied to this flange.
A method for manufacturing an electron gun assembly for a microwave tube, in which the lower end of the cathode sleeve and the lower end of the Wehnelt electrode are welded and fixed. [Embodiments of the Invention] Method for manufacturing an electron gun assembly for a microwave tube according to the present invention The cathode assembly 20 is constructed as shown in FIGS. 1(a) and 1(b), and the assembly of the cathode assembly 20 will be explained first. That is, 21 in the figure is an impregnated cathode substrate, and this cathode substrate 21 is manufactured as follows. Particle size is 3-10
After compression molding tungsten particles of μm into a rod shape, they are sintered in a reducing atmosphere. The pores of the sintered body thus obtained are impregnated with copper. The reason for impregnating copper is to facilitate cutting in the next step.

A porous tungsten sintered body impregnated with copper has an outer diameter of 4.3
The surface of the cathode substrate 21 of tm is cut using a lathe so that a groove is provided on the back surface with a radius of curvature of 10 m into which the cathode sleeve 22 made of molybdenum or the like is fitted.

Next, copper is removed by high temperature heating using a nitric acid and hydrogen furnace or the like. After the copper removal operation, an impregnated cathode substrate 21 is produced by melting and impregnating an electron-emitting substance such as BaO1At203 or CaO in a high-temperature reducing atmosphere.

In the figure, 22 is a cathode sleeve, and this cathode sleeve 2
2 has the same outer diameter as the impregnated cathode substrate 21, its length is 7.2fi, and its thickness is 50Rn. At one end of this cathode sleeve 22, at the end where the impregnated cathode substrate 21 is joined, a flange 22m that expands outward and has an outer diameter of 5.3 mm is integrally formed on the outside as shown in the figure. ing.

This cathode sleeve 22 and the impregnated cathode base 21 are joined using a molybdenum-ruthenium brazing material 23. This brazing material 23 is also applied to the back surface of the impregnated cathode substrate 21. This is to prevent the electron emitting substance impregnated into the impregnated cathode substrate 21 from diffusing into the heater embedding agent 25 and deteriorating the insulation between the heater 24 and the impregnated cathode substrate 21 . Further, the heater embedding agent 25 has an average particle size of 10Itr.
A mixture of n and 30 μm alumina powder at a weight ratio of 30% was kneaded with organic py/(diethyl carbonate containing 1% nitrocellulose), and the mixture was embedded in a vacuum at 1800°C for 2 hours. Obtained by sintering for a period of time.

The heater 24 is fixed in the cathode sleeve 22 using the heater embedding material 251fC, but the heater 24 is formed by coiling a rhenium-tungsten wire with a diameter of 0.1 mm as shown in the figure. The outer diameter of is 4.0 m.

After sintering the heater embedding agent 25, the cathode sleeve 22
A 1fC cylindrical support 26 is fitted and fixed by Rede welding, and this cylindrical support 26 is made of molybdenum with a thickness of 20 to 50 μm and a length of 2.5 μm. This cylindrical support body 26 may be made of the same material as the cathode sleeve 22,
It can also be made of different metals.

When the outer support cylinder 27 is attached coaxially to the outer periphery of the other end of the cylindrical support 26, the cathode assembly 20 is completed.

Next, a method of assembling the cathode assembly 20 and the Wehnelt electrode 28 will be explained in accordance with the first rotation.

In this invention, a jig 29 is used, but this jig 29 has no part that contacts the surface of the impregnated cathode structure 21. In other words, the distance between the surface of the impregnated cathode structure 21 and the Wehnelt electrode 28 is determined by using the flange 22a formed on the cathode sleeve 22, and the distance between the tip of the cylindrical portion 30 provided on the jig 29 and the tip of the Wehnelt electrode 28 is determined by using the flange 22a formed on the cathode sleeve 22. A certain dimension is determined in advance between the parts where the two parts come into contact with each other.

First, the Wehnelt electrode 28 is inserted into the jig 29, and the jig 3
1 to fix the Wehnelt electrode 28, and then insert the cathode structure 20f.Then, insert the cathode structure 20 using the cylindrical portion 30 as a guide so that the cathode structure 20 is grounded to the center of the Wehnelt electrode 28. do. Then, cathode structure 2
The tip of the cylindrical portion 30 of the jig 29 comes into contact with the 7 flange 22a formed by the 0 cathode sleeve 22FIC, and the insertion of the cathode assembly 20 is stopped at this point to obtain a predetermined dimension.

Thereafter, the end of the Wehnelt electrode 28 and one end of the cathode structure 20 are fixed by resistance welding, thereby completing the electron gun structure.

〔Effect of the invention〕

According to this invention, assembly can be performed without contacting the surface of the impregnated cathode substrate 21. That is, conventionally, assembly was carried out by contacting a part of the jig with the surface of the impregnated cathode substrate 21, but according to the present invention, assembly can be performed without touching the surface of the impregnated cathode substrate 2. It is. A thin film layer of Os, Ir, etc. is formed on the surface of the impregnated cathode substrate 21, and its effect is as described above, but it can be assembled without damaging or contaminating the surface. It is possible to make a microwave tube with the thin film still formed. Therefore, a uniform electron flow can be obtained without locally disturbing the electrons emitted from the surface of the impregnated cathode substrate 21, and excellent characteristics can be obtained.

Also, the same effect can be obtained by providing a similar material on the side surface of the impregnated cathode substrate 21;
Therefore, the electron emitting material is impregnated, and therefore the evaporation of the electron emitting material from the flange 22h occurs.
The Wehnelt electrode 28 adheres and is unfavorable in terms of characteristics.

On the other hand, since the length of the cylindrical portion 30 of the jig 29 is short, when the cathode assembly 20 is inserted, the jig 29 is likely to be eccentric.
The length of the cylindrical portion 30 is also long, and eccentricity can be prevented.
2ht- is provided, but the flange 22a is the cathode sleeve 22.
It may be provided at the other end and the same effect can be obtained.

[Brief explanation of the drawing]

Figures 1 (,) and (b) are cross-sectional views showing a method of manufacturing an electron gun assembly for a microwave tube according to an embodiment of the present invention, and Figures 2 (a) and Φ) are cross-sectional views of a conventional microwave tube. FIG. 3 is a cross-sectional view showing a method of manufacturing an electron gun assembly. 20... Cathode structure, 21... Impregnated cathode base, 22
...Cathode sleeve, 24...Heater, 25...Heater embedding agent, 26...Support, 27...Outer support cylinder. 28... Wehnelt electrode, 29.31... Jig, 3
0... Cylindrical part. Applicant's representative Patent attorney Takehiko Suzue Figure 1 (a)
) Figure 1 (1))

Claims (1)

[Claims] An impregnated cathode substrate is fixed to one end of a cathode sleeve that houses a heater therein and is fixed with a heater embedding agent, and further, the cathode sleeve is fixed to an outer support cylinder via a support, In the method for manufacturing an electron gun assembly for a microwave tube, which comprises a Wehnelt electrode coaxially provided outside the outer support cylinder and the impregnated cathode substrate, the end of the cathode sleeve to be joined to the impregnated cathode substrate A flange that expands outward is integrally formed in the part, and the cylindrical part of the alignment jig for the Wehnelt electrode is applied to this flange, and the lower end of the outer support cylinder and the lower end of the Wehnelt electrode are connected. A method for manufacturing an electron gun structure for a microwave tube, which is fixed by welding.