JP2001256883A - Impregnated cathode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an impregnated cathode permitting easy jointing to an electron gun with high accuracy in positioning. SOLUTION: A screw hole 13 for fitting to an electron gun is made on a flange 12. The screw hole and a screw hole made on the electron gun are aligned then a screw is driven in the common hole. Thus the impregnated cathode is joined to the electron gun. The periphery of the screw hole on the surface of the flange is provided with a projection 13a so that the contact area of the flange and the electron gun is limited. This device serves to reduce the heat leaking toward the electron gun to reduce the power consumption of the heater.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave electron tube such as a klystron having a high output, and more particularly to an impregnated cathode structure used for an electron gun.

[0002]

[Prior Art] In recent years, the output of microwave electron tubes such as klystrons has been increasing, and the output of microwave electron tubes used in nuclear fusion and particle accelerators has reached the megawatt level, and the output will continue to increase. Is expected to advance. Therefore, the emission value to be extracted from the cathode used in such a microwave electron tube is inevitably increased, and a higher current density of the cathode is required.

[0003] In response to such demands, it has been difficult to obtain a sufficient current value with a conventionally used oxide cathode and the operating voltage is high. Type cathodes are becoming popular. The impregnated cathode can operate at a current density of 3 A / cm ² , and has a life expectancy of 100,000 hours for use on a satellite. Because of these advantages, there is an increasing tendency to use impregnated cathodes in high power microwave electron tubes.

[0004] This impregnated cathode will be described with reference to FIG. In the figure, reference numeral 21 denotes a cathode disk made of porous tungsten having a porosity of 15 to 20%, and the holes of the cathode disk 21 are impregnated with an electron emitting material. Reference numeral 22 denotes a support cylinder made of Mo (molybdenum) for supporting the cathode disk 21.
Is brazed to the cathode disk 21 with a brazing material of a Mo-Ru (ruthenium) alloy. A heater 23 for assuring the operating temperature of the cathode disk 21 is accommodated in the support cylinder 22. An embedding material 24 such as alumina is contained in the support cylinder 22 in which the heater 23 is accommodated.
Is filled.

Further, in order to increase the thermal efficiency of such an impregnated cathode, there is known a method in which the heat of a heater is concentrated on a cathode disk using a reflector.

FIG. 4 shows an example of an impregnated cathode using this reflector. In the figure, reference numeral 31 denotes a cathode disk made of porous tungsten having a porosity of 15 to 20%, and the holes of the cathode disk 31 are impregnated with an electron emitting material. In the cathode disk 31, support cylinders 33, 34, and 35 forming a housing portion of the heater 32 are provided with Mo.
-Brazed with a Ru alloy brazing material. An embedding material 36 such as alumina is provided in a housing portion of the heater 32.
Is filled. A first reflector 37 is joined to one end of the support cylinder 33 by arc welding. Second
Is held at a predetermined distance from the first reflector 37 by a ring 39 welded to the support cylinder 35.

The support cylinder 33 is provided with a flange portion 40. A flange portion 41 for joining the flange portion 40 and the electron gun is provided with a support cylinder 42 made of a thin plate of a Mo-Re (rhenium) alloy. The upper and lower ends are brazed with a Mo-Ru-Ni alloy brazing material.

Next, a method of joining the structure of the impregnated cathode to the electron gun will be described.

First, the electron gun is placed on a turntable and fixed with a jig. Next, while rotating the impregnated cathode assembly and the electron gun, the position is adjusted so that the respective centers coincide. When the position is determined, temporary fixing is performed, and the periphery of the flange portion 41 of the impregnated cathode structure is joined to the electron gun portion by arc welding.

[0010]

In the step of joining the impregnated cathode structure and the electron gun section in this manner, the electron gun section is mounted on a turntable to align the respective core positions, and the electron gun section is mounted. And the operation of adjusting the position while rotating the impregnated cathode assembly was essential. However, this operation requires skill of an operator, and has a problem that efficiency is low.

Further, in the above-mentioned conventional impregnated cathode structure, there is a problem that heat loss from a joint portion with the electron gun portion is not small, and the heater consumes wasteful power accordingly.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an impregnated cathode assembly that can easily perform a joining operation with an electron gun with high positional accuracy.

Another object of the present invention is to provide an impregnated cathode assembly capable of reducing heat loss from a joint portion with an electron gun and reducing power consumption of a heater.

[0014]

According to a first aspect of the present invention, there is provided an impregnated cathode assembly, comprising: a cathode substrate impregnated with an electron-emitting substance; A heater for heating the cathode base at one end, a support cylinder housing the heater, and a screw hole attached to the other end of the support cylinder for joining with the electron gun. And a provided flange portion.

According to the present invention, by forming a flange having a screw hole by lathing or the like with sufficient dimensional accuracy, a screw hole or the like corresponding to the screw hole of the flange is formed on the electron gun side. Aligning the screw holes on the impregnated cathode assembly side and the electron gun side with each other and inserting the screws into these holes allows for easy and accurate positioning with the electron gun. Can be.

According to a second aspect of the present invention, the screw hole is provided with a convex portion projecting from a main surface of the flange portion. That is, in the impregnated cathode structure of the present invention, most of the main surface of the flange portion is not directly in contact with the electron gun portion but is supported by the convex portion, so that heat escaping to the electron gun portion can be reduced. As a result, the thermal efficiency is improved, and the power consumption of the heater can be reduced.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an impregnated cathode structure according to one embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a cathode disk made of porous tungsten having a porosity of 15 to 20%. The cathode disk 1 has an electron emission surface 1a having a predetermined curvature. The holes of the cathode disk 1 are impregnated with an electron-emitting substance. Here, a porosity of 15
Porous tungsten of about 20% is likely to be crushed when the electron emitting surface 1a is processed, and the crushing does not sufficiently impregnate the electron emitting material. To solve this,
In this embodiment, after the porous tungsten is impregnated with plastic and then the electron emitting surface 1a is processed,
The impregnated plastic is scattered by heat treatment in hydrogen or in a vacuum to obtain a cathode disk 1 with no crushed surface.

The cathode disk 1 is joined to support cylinders 2, 3, and 4 made of Mo or the like which form a housing for the heater 5. For joining the support cylinders 2, 3, and 4 to the cathode disk 1, a brazing material of a Ru-Mo alloy is used. The joining of the support cylinders 2, 3, and 4 to the cathode disk 1 prevents the electron emission material from seeping into the heater when the electron emission material is impregnated from the electron emission surface 1a of the cathode disk 1. For the purpose, it is possible to perform the crushing with the Ru—Mo alloy on the cathode disk 1 at the same time.

The heater 5 is, for example, a coil of a tungsten wire having a diameter of 1.5 mm. One end of the heater 5 is welded to the support cylinder 2 to make the heater 5 and the impregnated cathode the same potential.

After joining the support cylinders 2, 3, and 4 to the cathode disk 1, the support cylinders 2, 3, and 4 in which the heaters 5 are housed.
Is filled with a filling material 7 so that the heat of the heater 5 is efficiently transmitted to the cathode disk 1. As the filling material 7, for example, a material obtained by adding an insulating powder made of alumina to a material obtained by dissolving a binder in an organic solvent and stirring the mixture to form a paste is used. After filling the filling material 7,
The organic solvent is scattered by drying and then heated to 1800 to 1850 ° C. in vacuum or hydrogen to sinter the filling material 7. Thereafter, the reflection plate 8 is joined to the support cylinder 4 by arc welding.

The other end of the heater 5 is taken out of the buried portion 7 through an alumina tube 9 to prevent breakage near the boundary with the buried portion 7 and to insulate it from the cathode. Further, a plurality of reflectors 10 for improving thermal efficiency are joined to the support cylinder 2.

The support cylinder 4 is provided with a flange portion 14. The upper and lower portions of the support cylinder 11 made of a thin plate of a Mo-Re alloy are attached to a flange portion 12 for joining the flange portion 14 and an electron gun described later. The ends are brazed with a Mo-Ru-Ni alloy brazing material.

Finally, an electron-emitting substance is placed on the electron-emitting surface 1a of the cathode disk 1, and is placed in hydrogen at 1600 to 17
The mixture is heated to 00 ° C. and melted, and the holes of the cathode disk 1 are impregnated with an electron-emitting substance to complete an impregnated cathode assembly.

Here, the flange portion 1 for joining to the electron gun portion
Details of 2 will be described in detail.

The flange portion 12 is provided with a plurality of screw holes 13 for joining with the electron gun portion. In this example, four screw holes 13 are provided in the flange portion 12. On the other hand, although not shown, screw holes corresponding to the individual screw holes 13 of the flange portion 12 are provided also on the electron gun portion side, and the corresponding screw holes on the impregnated cathode assembly side and the electron gun portion side are provided. The impregnated cathode assembly and the electron gun unit can be joined by aligning the positions of the holes and inserting screws into the holes.

In this case, strict accuracy is required with respect to the positions and dimensions of the screw holes, but dimensional accuracy of about ± 0.02 mm can be guaranteed by manufacturing the flange portion 12 by lathing or the like. Therefore, it can be said that this is a sufficiently practical bonding method. Therefore, by using the impregnated cathode assembly of the present embodiment, it is possible to easily perform the joining operation with the electron gun unit with high positional accuracy without depending on the skill of the operator.

By the way, the heat of the impregnated cathode assembly escapes to the electron gun through the flange 12. In order to suppress this heat loss, the periphery of the screw hole 13 of the flange 12 is raised so that only the top surface of the projection 13a contacts the electron gun. The size of the contact surface with the electron gun is limited by the projection 13a. For example, in the case of the impregnated cathode assembly having an outer diameter of 70 mm, the contact area between the flange portion 12 and the electron gun portion was 29 cm ² , but the contact area around the screw hole 13 was 2 cm ^2.
It was able to reduce to the extent. Further, it was confirmed that the contact area of about 25% of the case where the cathode structure and the electron gun portion were fixed by arc welding the entire peripheral portion of the flange portion 12 was sufficient.

The case where the protruding portion 13a is formed concentrically around the screw hole 13 has been described above, but the protruding portion may be provided over the entire circumference with a constant width.

FIG. 2 shows the relationship between the heater power and the cathode assembly temperature by comparing the conventional example with the present embodiment. As can be seen from this graph, in the present embodiment, the heater power can be reduced by about 5 to 10% by reducing the heat loss by reducing the contact area between the flange 12 of the impregnated cathode assembly and the electron gun. That was confirmed.

[0032]

As described above, according to the impregnated cathode structure of the present invention, the screw hole for joining with the electron gun portion is provided in the flange portion for joining with the electron gun portion. The joining operation with the gun portion can be easily performed while ensuring high positional accuracy.

Further, according to the present invention, the convex portion for limiting the size of the contact surface with the electron gun portion is provided around the screw hole, so that the contact surface between the flange portion and the electron gun portion is formed. Since the size is limited to only the protrusions and the heat escaping to the electron gun can be reduced, the thermal efficiency can be improved and the power consumption of the heater can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an impregnated cathode structure according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a heater power and a cathode assembly temperature by comparing a conventional example with the present embodiment.

FIG. 3 is a diagram showing a conventional impregnated cathode structure.

FIG. 4 is a diagram showing a conventional large-diameter impregnated cathode assembly.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cathode disk 1a ... Electron emission surface 2, 3, 4 ... Support cylinder 5 ... Heater 7 ... Embedding material 8, 10 ... Reflector 11 ... Support cylinder 12 ... Flange part 13 ... Screw hole 13a ... Convex part

Claims (2)

[Claims] 1. A cathode base impregnated with an electron-emitting substance; a heater for heating the cathode base; a support cylinder supporting the cathode base at one end and containing the heater; And a flange attached to the other end and provided with a screw hole for joining to an electron gun. 2. The impregnated cathode assembly according to claim 1, wherein said screw hole is provided with a convex portion projecting from a main surface of said flange portion.