JP2019029260A - Impregnated cathode structure - Google Patents

Abstract

To provide an impregnated cathode structure capable of suppressing heat dissipation due to heat conduction and also capable of improving rigidity of a reflection cylinder.SOLUTION: An impregnated cathode structure according to an embodiment includes: a cathode substrate having an electron emission surface and impregnated with an electron emissive material; an outer cylinder provided to a surface on a side opposite to an electron emission surface of the cathode substrate; an inner cylinder provided at the inside of the outer cylinder; a heater provided between the inner cylinder and the outer cylinder; and a first reflection cylinder provided at the outside of the outer cylinder and having a projection projecting from a side part.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to an impregnated cathode assembly.

An electron gun having an impregnated cathode structure is used in a microwave electron tube that converts direct current electron energy such as a klystron or a gyrotron into microwave power.
For example, an impregnated cathode assembly used in an electron gun of a klystron has a cathode base, a heater, an insulating part, a reflector, a reflector, and the like.
The heater heats the cathode substrate impregnated with the electron-emitting material through the insulating portion. Electrons are emitted by heating the cathode substrate.
The reflecting cylinder has two roles. The first role is to support the cathode substrate. Therefore, it is preferable that the reflection cylinder has a large rigidity.
The second role is to suppress heat dissipation due to radiation from the insulating portion to the outside. If the heat radiation due to radiation can be suppressed, the heating efficiency of the cathode substrate can be increased.
However, in order to support the cathode substrate, the reflecting cylinder is joined to the cathode substrate. For this reason, when the reflection tube is provided, heat radiation due to radiation from the insulating portion to the outside can be suppressed, but there is a problem that heat radiation due to heat conduction from the cathode base to the outside occurs. In this case, if the thickness of the reflecting cylinder is increased in order to increase the rigidity of the reflecting cylinder, the heat radiation due to heat conduction increases.
Therefore, it has been desired to develop an impregnated-type cathode assembly that can suppress heat dissipation due to heat conduction and can improve the rigidity of the reflecting cylinder.

JP 2011-129361 A

  The problem to be solved by the present invention is to provide an impregnated-type cathode assembly that can suppress heat radiation due to heat conduction and can improve the rigidity of a reflecting tube.

  The impregnated-type cathode assembly according to the embodiment has an electron emission surface, a cathode base impregnated with an electron-emitting material, an outer cylinder provided on a surface of the cathode base opposite to the electron emission surface, A first cylinder having an inner cylinder provided on the inner side of the outer cylinder, a heater provided between the inner cylinder and the outer cylinder, and a protrusion provided on the outer side of the outer cylinder and protruding from a side portion; And a reflection tube.

It is a typical fragmentary sectional view for illustrating the impregnation type cathode structure concerning this embodiment. It is a model perspective view for illustrating a reflective cylinder. It is an expanded view of a reflecting cylinder. It is a typical fragmentary sectional view for illustrating the impregnation type cathode structure concerning other embodiments. It is a model perspective view for illustrating the reflective cylinder which concerns on other embodiment. It is an expanded view of the reflective cylinder which concerns on other embodiment. It is a model perspective view for illustrating the projection part concerning other embodiments.

Hereinafter, embodiments will be illustrated with reference to the drawings. In addition, in each drawing, the same code | symbol is attached | subjected to the same component and detailed description is abbreviate | omitted suitably.
The impregnated-type cathode assembly 1 according to the present embodiment can be used for an electron gun of a klystron, for example.
However, the use of the impregnated-type cathode assembly 1 is not limited to the klystron.

FIG. 1 is a schematic partial cross-sectional view for illustrating an impregnated cathode assembly 1 according to the present embodiment.
As shown in FIG. 1, the impregnated-type cathode assembly 1 includes a cathode base 10, a cylinder 20, a heater 30, an insulating portion 40, a reflector 50, a flange 60, and a reflector 70 (as an example of a first reflector). Equivalent).

The cathode substrate 10 is impregnated with an electron emitting substance. The cathode substrate 10 has an electron emission surface 11. The cathode substrate 10 can be made of, for example, porous tungsten (W) having a porosity of about 20%. The cathode substrate 10 has, for example, a disk shape. The diameter of the cathode substrate 10 can be about 70 mm. The cathode substrate 10 is formed with an electron emission surface 11 having a predetermined curvature and recessed in a curved shape. The holes of the cathode substrate 10 are impregnated with an electron emitting material including, for example, barium oxide (BaO), calcium oxide (CaO), aluminum oxide (Al ₂ O ₃ ), and the like.

In addition, when the electron emission surface 11 is processed, voids may be crushed. When clogging occurs, the electron emitting material may not be sufficiently impregnated in the pores. In order to prevent this, it is desirable that the holes of the cathode substrate 10 are impregnated with the electron emitting material as follows.
First, before processing the electron emission surface 11, the pores of the cathode substrate 10 are impregnated with plastic. Next, after processing the electron emission surface 11, the cathode substrate 10 is heated in a hydrogen atmosphere or in a vacuum to scatter the impregnated plastic.
Thereafter, the holes of the cathode substrate 10 are impregnated with an electron emitting substance.
In this way, the holes of the cathode substrate 10 can be sufficiently impregnated with the electron emitting substance.

  The cylindrical body 20 is provided on the surface 12 of the cathode base 10 opposite to the electron emission surface 11. The cylinder 20 stores the heater 30 and the insulating portion 40 in a storage space 21 formed therein. The cylinder 20 has an outer cylinder 22 and an inner cylinder 23.

  The outer cylinder 22 and the inner cylinder 23 can be formed from molybdenum (Mo). The outer cylinder 22 and the inner cylinder 23 have a cylindrical shape, for example. The inner cylinder 23 is disposed inside the outer cylinder 22 so as to be coaxial (concentric) with the outer cylinder 22. Therefore, an annular storage space 21 is formed between the outer wall of the inner cylinder 23 (wall surface on the outer cylinder 22 side) and the inner wall of the outer cylinder 22 (wall surface on the inner cylinder 23 side). For example, the inner cylinder 23 can have a diameter of about 20 mm, an axial length of about 15 mm, and a wall thickness of about 2 mm.

  One end of the storage space 21 is closed by the cathode base 10. The cathode base 10 is bonded to one end of the outer cylinder 22 and the inner cylinder 23. For example, one end of the outer cylinder 22 and the inner cylinder 23 and the surface 12 of the cathode base 10 are brazed using a ruthenium-molybdenum (Ru-Mo) alloy.

  The heater 30 is provided between the inner cylinder 23 and the outer cylinder 22. The heater 30 heats the cathode base 10 via the insulating part 40. The heater 30 can be a filament made of a linear member. The linear member can be, for example, a tungsten (W) wire having a cross-sectional dimension (wire diameter) of 1.5 mm. An intermediate portion (heat generation portion) 31 of the heater 30 has a coil shape. The intermediate portion 31 is provided inside the insulating portion 40. For example, the central axis of the intermediate portion 31 extends along the circumferential direction of the inner cylinder 23.

One end 32 of the heater 30 is electrically connected to the inner cylinder 23. Therefore, the heater 30, the cylindrical body 20, and the cathode base 10 are at the same potential.
The other end 33 of the heater 30 extends outside the impregnated-type cathode assembly 1 through the inside of the insulating tube 34. The end portion 33 of the heater 30 is electrically connected to a power supply device (not shown).

  The insulating tube 34 is provided on the opposite side of the cylindrical body 20 from the side on which the cathode base 10 is provided. The insulating tube 34 is provided to prevent the end portion 33 from breaking near the surface of the insulating portion 40 and to insulate the heater 30 and the reflecting plate 50 from each other. The insulating tube 34 can be formed from alumina (aluminum oxide) or the like, for example.

  The insulating unit 40 transmits heat from the heater 30 to the cathode base 10. The insulating unit 40 holds the heater 30 stored in the storage space 21. The insulating unit 40 insulates the heater 30. The insulating portion 40 is filled in the storage space 21 in which the intermediate portion 31 of the heater 30 is stored without a gap. The insulating portion 40 can be, for example, an alumina sintered body.

The reflection plate 50 is provided to suppress heat radiation from the insulating portion 40 to the outside and increase the heating efficiency of the cathode substrate 10 by radiation.
The reflection plate 50 can be formed from molybdenum (Mo). The reflection plate 50 can be an annular plate-like body. The reflection plate 50 is provided so as to close the opening of the storage space 21 on the side opposite to the side where the cathode substrate 10 is provided. The reflector 50 can be welded to the outer cylinder 22 by arc welding.

Moreover, the reflecting plate 51 and the reflecting plate 52 can be further provided.
The reflection plate 51 can be provided on the opposite side of the reflection plate 50 from the insulating portion 40 side. The reflection plate 51 can be an annular plate-like body. The reflection plate 52 can be provided on the opposite side of the reflection plate 51 from the insulating portion 40 side. The reflector 52 can be a disc. The reflecting plate 51 and the reflecting plate 52 can be formed from, for example, molybdenum (Mo). An annular spacer 53 is provided between the reflecting plate 50 and the reflecting plate 51 and between the reflecting plate 51 and the reflecting plate 52. Therefore, a predetermined gap can be provided between the reflecting plate 50 and the reflecting plate 51 and between the reflecting plate 51 and the reflecting plate 52. If the reflecting plate 51 and the reflecting plate 52 are provided, heat radiation from the insulating portion 40 to the outside can be further suppressed.

  The flange 60 faces the surface 12 of the cathode substrate 10. The flange 60 is provided on the opposite side of the reflecting plate 52 from the insulating portion 40 side. The flange 60 can be an annular plate-like body. The flange 60 can be formed from, for example, molybdenum (Mo). The impregnated cathode assembly 1 is fixed to an electron gun portion (not shown) via a flange 60.

  For example, the reflecting tube 70 may have a cylindrical shape. The reflecting cylinder 70 can be formed using, for example, a thin plate of rhenium-molybdenum (Re-Mo) alloy. The reflection cylinder 70 is disposed outside the outer cylinder 22 with a space from the outer cylinder 22. One end of the reflecting tube 70 (the end on the cathode base 10 side) is brazed to the outer tube 22. The other end of the reflecting tube 70 (the end opposite to the cathode base 10 side) is brazed to the flange 60. The brazing can be performed using, for example, a ruthenium-molybdenum-nickel (Ru-Mo-Ni) alloy.

If the reflecting cylinder 70 is provided, heat dissipation due to radiation from the insulating portion 40 (outer cylinder 22) to the outside can be suppressed. Therefore, the heating efficiency of the cathode substrate 10 can be improved. Further, if the reflecting cylinder 70 is provided, the cathode base 10 can be supported when the flange 60 is fixed to the electron gun portion.
Considering that the cathode substrate 10 is supported, it is preferable that the reflecting cylinder 70 has a higher rigidity. In this case, if the thickness of the reflecting cylinder 70 is increased, the rigidity of the reflecting cylinder 70 can be increased.
On the other hand, one end of the reflecting cylinder 70 is joined to the cathode base 10 via the outer cylinder 22. The other end of the reflecting tube 70 is joined to the electron gun unit via the flange 60. Therefore, the heat of the cathode base 10 is transmitted to the electron gun section through the outer cylinder 22, the reflecting cylinder 70, and the flange 60.
That is, when the reflection tube 70 is provided, heat radiation due to radiation from the insulating portion 40 to the outside can be suppressed, but there is a problem that heat radiation due to heat conduction from the cathode base 10 to the outside occurs. In this case, if the thickness of the reflecting cylinder 70 is increased in order to increase the rigidity of the reflecting cylinder 70, heat dissipation due to heat conduction increases.

Therefore, the reflecting tube 70 according to the present embodiment is provided with a protruding portion 70a.
FIG. 2 is a schematic perspective view for illustrating the reflecting cylinder 70.
FIG. 3 is a development view of the reflecting cylinder 70.
As shown in FIG. 2, the reflecting tube 70 has a cylindrical shape and is provided with a protruding portion 70 a that protrudes from a side portion (body portion). Although the number of the protrusions 70a is not particularly limited, it is preferable that a plurality of protrusions 70a are provided. If the plurality of projecting portions 70a are provided, it is easy to increase the rigidity of the reflecting tube 70. Further, the arrangement of the plurality of protrusions 70a is not particularly limited, but the plurality of protrusions 70a are preferably provided at equal intervals. If the plurality of projecting portions 70a are provided at equal intervals, it becomes easy to make the rigidity of the reflecting cylinder 70 uniform. There is no particular limitation on the planar shape of the protrusion 70a. The planar shape of the protrusion 70a can be, for example, an oval as illustrated in FIGS. 2 and 3, or a circle or a polygon.

  Further, the protruding portion 70 a may protrude outward from the side of the reflecting tube 70, or may protrude inward from the side of the reflecting tube 70. However, as shown in FIG. 1, the distance between the protruding portion 70 a and the outer cylinder 22 can be increased if the protruding portion 70 a protrudes outward from the side portion of the reflecting tube 70. Therefore, it becomes easy to suppress the heat radiation by radiation.

The wall thickness of the protrusion 70a can be made substantially the same as the wall thickness of the reflection tube 70 other than the protrusion 70a. When the protruding portion 70a protrudes outward from the side portion of the reflecting tube 70, the protruding portion 70a is formed such that a part of the outer surface of the reflecting tube 70 is convex and the outer surface is convex. In the formed part, the inner surface of the reflecting cylinder 70 can be formed in a concave shape.
The protrusion 70a can be formed by, for example, press working (embossing) using a press stamping die.

The reflection cylinder 70 having the plurality of protrusions 70a can be formed as follows, for example.
First, a belt-like plate having a thickness of about 0.1 mm is prepared. The material of the strip-shaped plate can be, for example, rhenium-molybdenum.
Next, as shown in FIG. 3, the plurality of protrusions 70a are formed at regular intervals by embossing.
Next, as shown in FIG. 2, the belt-like plate on which the plurality of protrusions 70a are formed is rounded into a cylindrical shape, and the end portions 70b of the belt-like plate are overlapped.
Next, the overlapped portions are joined by resistance welding.
As described above, it is possible to form the reflecting cylinder 70 having the plurality of projecting portions 70a.

  If the reflecting cylinder 70 having the protrusion 70a is used, the rigidity of the reflecting cylinder 70 can be increased. For this reason, it is possible to reduce the wall thickness compared to a reflecting tube that does not have the protruding portion 70a. If the thickness can be reduced, the area (cross-sectional area) of the end of the reflecting cylinder 70 on the cathode base 10 side can be reduced, so that the amount of heat transferred from the cathode base 10 to the reflecting cylinder 70 can be reduced. .

According to the knowledge obtained by the present inventor, when the thickness of the reflecting cylinder having no protrusion 70a is 0.15 mm, the thickness of the reflecting cylinder 70 having the same rigidity is set to 0.1 mm or less. I was able to. Therefore, the cross-sectional area of the reflecting cylinder 70 can be reduced by 33% or more.
Furthermore, if the protrusion 70a is provided, the heat transfer distance can be increased, so that the amount of heat transferred to the flange 60 (electron gun portion) can be reduced.
As described above, if the reflecting cylinder 70 has the projecting portion 70a, heat radiation due to heat conduction can be suppressed, and the rigidity of the reflecting cylinder 70 can be improved.

FIG. 4 is a schematic partial cross-sectional view for illustrating an impregnated-type cathode assembly 1a according to another embodiment.
FIG. 5 is a schematic perspective view for illustrating a reflecting cylinder according to another embodiment.
FIG. 6 is a development view of a reflecting tube according to another embodiment.
FIG. 7 is a schematic perspective view for illustrating a protrusion 70a1 according to another embodiment.
As shown in FIG. 4, the impregnated-type cathode assembly 1a is further provided with a reflection cylinder 71 (corresponding to an example of a second reflection cylinder).

  As shown in FIG. 5, the reflecting cylinder 71 can be, for example, a cylinder. The reflection cylinder 71 can be formed by using, for example, a rhenium-molybdenum alloy thin plate. The thickness of the reflecting cylinder 71 can be the same as the thickness of the reflecting cylinder 70.

  The reflection cylinder 71 is provided outside the reflection cylinder 70. The reflection cylinder 71 is provided so as to surround the side portion of the reflection cylinder 70. In this case, if the protruding portion 70 a protrudes outward from the side portion of the reflecting tube 70, it is possible to prevent the outer surface of the reflecting tube 70 and the inner surface of the reflecting tube 71 from coming into close contact with each other. That is, a gap can be secured between the portion of the reflecting tube 70 where the protruding portion 70 a is not provided and the inner surface of the reflecting tube 71. In this case, the inner surface of the reflecting cylinder 71 and the protruding portion 70a of the reflecting cylinder 70 may be in contact with each other or may not be in contact. However, if the inner surface of the reflecting cylinder 71 and the protrusion 70a of the reflecting cylinder 70 are not in contact, the amount of heat transferred from the reflecting cylinder 70 to the reflecting cylinder 71 can be reduced.

Since the reflecting cylinder 71 does not support the cathode base 10, one end of the reflecting cylinder 71 (the end on the cathode base 10 side) can be prevented from contacting the outer cylinder 22. If the reflecting cylinder 71 and the outer cylinder 22 are not in contact, the amount of heat transferred from the cathode base 10 to the reflecting cylinder 71 by heat conduction can be eliminated.
As will be described later, the reflecting cylinder 70 and the reflecting cylinder 71 may be integrally formed. In that case, the other end (the end opposite to the cathode base 10 side) of the reflecting cylinder 71 may be brazed to the flange 60 or may not be brazed. Brazing can be performed using, for example, a ruthenium-molybdenum-nickel alloy.

  Since the reflecting cylinder 71 does not support the cathode substrate 10, the rigidity of the reflecting cylinder 71 can be made smaller than the rigidity of the reflecting cylinder 70. Therefore, it is possible not to provide the protruding portion 70a in the reflecting cylinder 71. In this case, the thickness of the reflecting cylinder 71 can be the same as the thickness of the reflecting cylinder 70.

  Further, when the reflection cylinder 71 surrounding the side portion of the reflection cylinder 70 is provided, a hole is provided in the top surface of the protruding portion 70a, or a part of the side portion of the reflection cylinder 70 is formed as illustrated in FIG. The protrusion 70a1 may be bent.

The reflecting cylinder 70 and the reflecting cylinder 71 can be integrally formed as follows, for example. First, a belt-like plate having a thickness of about 0.1 mm is prepared. The material of the strip-shaped plate can be, for example, rhenium-molybdenum.
Next, as shown in FIG. 6, a plurality of protrusions 70a are formed at equal intervals in a partial region of the belt-like plate by embossing.
Next, as shown in FIG. 5, the area | region in which the some protrusion part 70a of the strip | belt-shaped board was formed is rounded cylindrically, and also the several protrusion part 70a of a strip | belt-shaped board is formed in the outer side. The unexposed region is rounded and the end portions 71a of the belt-like plate are overlapped.
Next, the overlapped portions are joined by resistance welding.
As described above, the reflecting cylinder 70 having the plurality of projecting portions 70a and the reflecting cylinder 71 can be integrally formed.

Note that the reflecting tube 70 having the plurality of protruding portions 70 a and the reflecting tube 71 may be formed separately, and the respective end portions may be joined to the flange 60.
If the reflecting cylinder 71 surrounding the side portion of the reflecting cylinder 70 is provided, heat radiation due to radiation from the reflecting cylinder 70 to the outside can be suppressed. Therefore, the heating efficiency of the cathode substrate 10 can be further improved.

Next, a method for manufacturing the impregnated-type cathode assembly 1 according to the present embodiment will be illustrated.
First, the cylindrical body 20 is placed on the surface 12 of the cathode base 10 that is not impregnated with the electron emitting substance, and a ruthenium-molybdenum alloy is applied to the junction between the negative electrode base 10 and the cylindrical body 20. Similarly, ruthenium-molybdenum alloy is applied to the surface 12 of the cathode substrate 10. After the application, the ruthenium-molybdenum alloy is dissolved, the cathode base 10 and the cylinder 20 are joined, and a ruthenium-molybdenum alloy film is formed on the surface 12 of the cathode base 10. This ruthenium-molybdenum alloy film prevents the electron emitting material from oozing out from the surface 12 of the cathode substrate 10 into the storage space 21 when the cathode emitting substrate 11 is impregnated with the electron emitting material. Provided.

Next, the heater 30 is held at a predetermined position in the storage space 21 by using a jig, and the insulating portion 40 is filled in the storage space 21. The insulating part 40 can be formed, for example, by pouring a paste-like material into the storage space 21 and then drying and sintering.
The pasty material can be produced, for example, by adding powdery alumina to an organic solvent containing a binder and stirring it.
Moreover, drying is performed in order to disperse the organic solvent contained in the paste-like material.
In the sintering, for example, heating is performed at about 1800 ° C. to 1850 ° C. in a vacuum or a hydrogen atmosphere.

Next, the end 32 of the heater 30 is welded to the inner cylinder 23.
Next, the reflecting plate 50 is welded to the cylindrical body 20, and the reflecting plate 51 is welded to the reflecting plate 50 via the spacer 53.
Next, the reflecting plate 52 is welded to the reflecting plate 51 through the spacer 53.

Next, one end portion (end portion on the cathode base 10 side) of the reflection cylinder 70 is installed outside the outer cylinder 22, and ruthenium-molybdenum-nickel alloy is applied to the joint portion between the reflection cylinder 70 and the outer cylinder 22. Apply. Similarly, a flange 60 is disposed at the other end (the end opposite to the cathode substrate 10 side) of the reflecting cylinder 70, and ruthenium-molybdenum-nickel alloy is applied to the joint between the reflecting cylinder 70 and the flange 60. Apply. After the application, the ruthenium-molybdenum-nickel alloy is dissolved, and the reflecting cylinder 70, the outer cylinder 22 and the flange 60 are joined.
As illustrated in FIGS. 5 and 6, when the reflecting tube 70 and the reflecting tube 71 are integrally formed, the reflecting tube 71 is held by the reflecting tube 70.
When the reflecting cylinder 70 and the reflecting cylinder 71 are formed separately, the end of the reflecting cylinder 71 (the end opposite to the cathode substrate 10 side), the flange 60, and the like Join.

Finally, the cathode substrate 10 is impregnated with an electron emitting material, whereby the impregnated cathode assembly 1 is completed.
The impregnation of the electron emitting substance can be performed as follows.
First, an electron emitting material is placed on the electron emission surface 11 of the cathode substrate 10.
Next, the electron emitting substance is heated to 1600 ° C. to 1700 ° C. in a hydrogen atmosphere. Then, the electron emitting material is melted and impregnated in the cathode substrate 10.

  As mentioned above, although several embodiment of this invention was illustrated, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, changes, and the like can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and equivalents thereof. Further, the above-described embodiments can be implemented in combination with each other.

  DESCRIPTION OF SYMBOLS 1 Impregnation type | mold cathode structure, 10 cathode base | substrate, 11 electron emission surface, 20 cylinder, 21 storage space, 22 outer cylinder, 23 inner cylinder, 30 heater, 40 insulation part, 50-52 reflector, 60 flange, 70 reflector , 70a Projection part, 70a1 Projection part, 71 Reflector tube

Claims (5)

A cathode substrate having an electron emission surface and impregnated with an electron emitting material;
An outer cylinder provided on a surface of the cathode substrate opposite to the electron emission surface;
An inner cylinder provided inside the outer cylinder;
A heater provided between the inner cylinder and the outer cylinder;
A first reflecting cylinder provided on the outer side of the outer cylinder and having a protruding portion protruding from a side portion;
An impregnated cathode assembly comprising:   The impregnated-type cathode assembly according to claim 1, wherein a plurality of the protrusions are provided.   The impregnated-type cathode assembly according to claim 2, wherein the plurality of protrusions are provided at equal intervals.   The impregnated-type cathode assembly according to any one of claims 1 to 3, further comprising a second reflecting cylinder provided outside the first reflecting cylinder.   The impregnated-type cathode assembly according to claim 4, wherein the first reflecting cylinder and the second reflecting cylinder are integrally formed.

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