JPS61216223A - Impregnated type cathode composition - Google Patents

Abstract

PURPOSE:To acquire an impregnated type cathode composition with little thermal loss, and with a stable performance in a low power expenditure, by furnishing a heat conduction decreasing portion at the connection between a heat container and a cathode supporter. CONSTITUTION:This cathode composition has a cathode base 2 with an electron radiating surface 1 at one end, a heater member 10 installed at the other end of the cathode base 2, and a supporter 11 to support the cathode base 2 and the heater member 10, arranged between the heater member 10 and a supporting tube 5. The supporter 11 is welded to the heater container 14, and the supporter tube 5 is welded to the supporter 11. Since a heat conduction decreasing portion is furnished at the connection between the side of the opening at the other end of the heater container, one end of which is installed to the cathode base, and the supporter, to decrease the thermal loss escaping through the supporter from the heater container, the impregnated type cathode composition with a stable performance in a low expenditure of power can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an impregnated cathode structure suitable for electron tubes such as traveling wave tubes and klystrons that require high reliability.

[Technical background of the invention and its problems]

High-power traveling wave tubes mounted on artificial satellites are required to have a high current density, and an impregnated cathode structure is used as a suitable cathode. What is particularly required of this cathode for use in satellites is, of course, a long life.
In addition, it uses solar cells as a power source, so it has low power consumption, and is resistant to shocks during satellite launches.In other words, if the heater embedding material is deformed or falls off due to shocks during launch, the heater's heat generation will be effective. It is necessary to have sufficient strength to withstand impact, since the electron beam may no longer be transmitted, causing the cathode temperature to drop, or the falling embedding agent may become a foreign object in the tube and cause the electron tube to operate abnormally.

However, in the conventional impregnated cathode structure, as shown in FIG. 1) A heater part (3) is attached to the other end of the cathode base (2).
is provided, and a support body (
The heater container (6) is formed of a cylindrical body with a certain wall thickness, and the heater container (6) is supported by the support tube (5) through the support tube (5) so as to surround the opening side of the heater container (6). (4)
Since the heater container (6) is welded, there is a large heat loss escaping from the heater container (6) through the support (4), resulting in wasted power consumption.

Also, a heater (7) inserted into the heater container (6)
is embedded in an embedding agent (8) filled to a certain depth from the open end of the heater container (6). Alumina powder made into a slurry by adding an organic binder and an organic solvent is poured into the opening of the heater container (6), and after drying, the excess portion is removed from the opening using a pointed metal rod or glass tip. Since the amount of filling is adjusted by the method, especially when the diameter of the heater container (6) is reduced to about 3 to 5III11, the legs of the heater (7) extending from the opening are avoided and firmly bound with the binder. It was difficult to remove the alumina powder.

Therefore, the amount of the embedding agent (8) is not constant, and the heater (7)
) After turning on, the time it takes for the cathode substrate (2) to reach the operating temperature and the power consumption of the heater (7) vary, and the surface after removing excess alumina is not smooth or flat, so it may fall off due to impact. There was also the problem that it was easy.

[Purpose of the invention]

The object of the present invention is to construct an impregnated cathode structure that has little heat loss and operates stably with low power consumption.

[Summary of the invention]

A cathode substrate in which the pores of a high-melting point porous metal substrate are impregnated with an electron emitting substance and one end surface serves as an electron emitting surface; one end is attached to the other end surface of the cathode substrate, and the other end is open. a heater container, a heater inserted into the heater container, and the heater container is filled and buried in the heater container so that an unfilled part is one inch deep from the open end of the heater container. a heater section having an embedding agent;
In an impregnated cathode assembly comprising a cathode support joined to the side surface of the opening end of the heater container, a heat conduction reducing portion is provided at the joint between the heater container and the cathode support to reduce heat loss. , configured to operate with low power consumption.

[Embodiments of the invention]

Hereinafter, the present invention will be described based on embodiments with reference to the drawings.

FIG. 1 shows an impregnated cathode structure which is one embodiment of the present invention. This cathode structure includes a cathode base (2) whose one end surface is an electron emission surface (1), a heater part (10) attached to the other end of this cathode base (2), and a heater part (10) attached to the other end of this cathode base (2). and a support body (11) that is interposed between the support tube (5) and supports the cathode base body (2) and the heater section (10).

The cathode substrate (2) has BaO1CaO1i20. The electron emitting surface (1) is formed into a concave spherical shape on one end surface, and the other end surface is impregnated with an electron emitting material consisting of a heater portion (10). A section has been established.

The heater part (10) is formed into a cylindrical shape that fits into the small diameter part of the cathode base (2), and is made of a brazing material (made of molybdenum-ruthenium alloy) that protects the other end surface of the cathode base (2).
A heater container (14) made of molybdenum coaxially joined to the cathode substrate (2) by a heater container (13);
A coil-shaped heater (7) is inserted into the heater container (14) so that a pair of legs (15) extend from the opening of the heater (14).
) and an embedding agent (
8). The heater container (14) of this embedding agent (8)
) The exposed surface (J6) facing the opening of the heater container (1
4) is located at a certain depth from the opening end.

The side wall of the cylindrical heater container (14) is formed to have a certain thickness, and the periphery of the embedding agent (8) in particular is not filled with the embedding agent (8) on the other end opening side. A plurality of through holes (17) are formed in contact with the exposed surface of 8).

The support body (11) is formed in a truncated conical shape with a small diameter end that fits on the outside of the heater container (14), and the small diameter end fits into the unfilled part of the heater container (14). mated,
It is attached to the heater container (14) by welding. The other end of this support (11) is welded to a support (5) surrounding the heater container (14), and the cathode base (2) and heater section (10) are attached to this support (11).
It is supported by the support tube (5) via the support tube (5).

This impregnated cathode structure is manufactured as follows.

First, tungsten powder with a predetermined particle size is compressed and sintered, and then the pores are impregnated with copper and cut into a predetermined shape. Thereafter, the impregnated copper is removed by high-temperature heat treatment using nitric acid and a hydrogen furnace to form a porous metal substrate. Next, a brazing material made of a molybdenum-ruthenium alloy is applied to the end surface of the small-diameter side of this metal base, and a heater container (14), which has been previously formed into a predetermined shape by machining, is fitted onto the brazing material. Melt and braze the heater container (14) to the metal substrate.

Next, a heater (7) is inserted into this heater container (14), and an organic binder and an organic solvent are added to fill the alumina powder which has become slurry. After drying, the surface of the filled alumina powder is heated. It is removed using a sharp metal rod or a glass sprocket until it reaches a height that touches the periphery of the through hole (17) formed in the container (14). Thereafter, this embedding material is sintered to form the heater part (10).

Next, the support (11) is welded to the heater container (14), and the support tube (5) is welded to the support (11), and an electron emitting material made of Bad, CaO1AQ203, etc. is melted to the metal base. Impregnate. Note that this impregnation with the electron emitting substance may be performed before attaching the heater container (14) to the metal base.

When the impregnated cathode structure is configured as described above, the heater part (
10) Heat loss can be reduced.

That is, as is clear from the relationship between the heater voltage and the cathode temperature shown in FIG. 2, when the conventional impregnated cathode structure (shown in FIG. 6) is constructed without a support attached to the heater part and a voltage is applied to the heater, The cathode temperature changes as shown by curve (A), but when a support is attached to it, it changes as shown by curve (B). That is, when the heater voltage is low, it is lower than the curve (A), and when the heater voltage is high, it is higher than the curve (A). This means that when a support is attached to the heater vessel, heat loss will occur through the support from the edge of the heater vessel, and conversely, as the heater voltage increases, thermal efficiency will be reduced due to reflection from the support. It means things will get better. However, as shown in the above example,
When a plurality of through holes (17) are provided at the end of the heater container (14) and the support body (11) is attached, the through holes (17) are formed at the end of the heater container (14).
) forms the part where the heat conduction decreases, and the curve (C)
As shown in , thermal efficiency is improved regardless of the heater voltage.

Furthermore, by providing a through hole (17) at the end of the heater container (14), a surplus portion of the implant filled in the heater container (14) can be drained from the opening at the other end and the side wall of the heater container (14). The exposed surface (16) of the embedding agent (8) can be easily removed from the through hole (17), and the position of the exposed surface (16) of the embedding agent (8) can be determined based on the periphery of the through hole (17). The amount can be kept constant. Therefore, by keeping the heat capacity of the heater part (10) constant, the power consumption of the heater (7)
) It is possible to create a cathode structure in which the time required for the cathode to reach the operating temperature after turning on does not vary.

Furthermore, a through hole (
Excess alumina is removed from the exposed surface (16).
) can be made smooth and flat, making it possible to create a cathode structure in which the embedding agent (8) is difficult to fall off even if an impact is applied.

Next, other embodiments will be described.

In the above embodiment, a through hole was provided at the end of the heater container to serve as a heat conduction reducing section.
19) may be used, and the same effect can be achieved. Also, as shown in Figures 4 and 5,
It may also be constructed of a thin walled portion consisting of a recessed hole (20a) or a cutout groove (20b).

Further, in each of the above embodiments, the heater container is provided with a heat conduction reducing portion consisting of a through hole, a notch, a recessed hole, a cutout groove, etc. It may be provided on both sides of the body.

The support is usually made of molybdenum, which has relatively good thermal conductivity.
It is made of tantalum, etc., but even if it is made of a material with low thermal conductivity such as stainless steel, it will be even better. A heat conduction reducing part is provided at the joint between the and the support,
[-Since the structure is configured so that heat loss escaping from the container through the support is reduced, an impregnated cathode structure that operates stably with low power can be obtained.

[Brief explanation of drawings]

FIG. 1 is a partially cross-sectional front view of an impregnated cathode structure according to an embodiment of the present invention, and FIG. Graphs shown for comparison, FIGS. 3 to 5 are front views showing main parts of other embodiments of the present invention in two-part cross section, and FIG. 6 is a sectional view of a conventional impregnated cathode structure. be. (1) ...electron emission surface (2) ...cathode base (7) ...heater (8) ...embedding agent (10) ...heater part (11) ...support 1l −

Claims (8)

[Claims] (1) A cathode substrate in which the pores of a high-melting point porous metal substrate are impregnated with an electron-emitting substance and one end surface serves as an electron-emitting surface, and one end is attached to the other end of this cathode substrate and the other end is open. A cylindrical heater container, a heater inserted into the heater container, and a heater container filled with the heater container so as to form an unfilled portion of a certain depth from the open end of the heater container, and the heater buried therein. and a cathode support joined to a side surface of the opening end of the heater container, and a heat conduction reducing portion is provided at the joint between the heater container and the cathode support. An impregnated cathode structure characterized by: (2) The impregnated cathode assembly according to claim 1, wherein the heat conduction reducing portion is provided in the heater container. (3) The impregnated cathode assembly according to claim 2, wherein the heat conduction reducing portion is in contact with an exposed surface of the embedding agent formed at a certain depth from the open end of the heater container. (4) The impregnated cathode assembly according to claim 1, wherein the heat conduction reducing portion is provided on the cathode support. (5) The impregnated cathode assembly according to claim 1, wherein the heat conduction reducing portion is provided on both the heater container and the cathode support. (6) The impregnated cathode assembly according to claim 1, wherein the heat conduction reducing portion has a through hole. (7) The impregnated cathode assembly according to claim 1, wherein the heat conduction reducing portion has a notch. (8) The impregnated cathode assembly according to claim 1, wherein the heat conduction reducing portion has a thin wall portion.