JP6735162B2 - Impregnated cathode assembly - Google Patents

Description

Embodiments of the present invention relate to an impregnated cathode assembly.

An electron gun having an impregnated cathode structure is used in an electron tube such as a klystron or a traveling wave tube that converts direct-current electron energy into microwave power.
The impregnated cathode structure is provided with a disk-shaped cathode base body, a cylinder body having an inner cylinder and an outer cylinder, a heater housed in a space formed by the cathode base body and the cylinder body, an embedded portion, and the like. There is.
Further, one end of the heater is welded to the inner cylinder or the outer cylinder of the cylindrical body.
Here, the thermal expansion coefficient of the tubular body is different from the thermal expansion coefficient of the embedded portion. Therefore, when heating is performed by the heater, a difference occurs between the thermal expansion amount of the tubular body and the thermal expansion amount of the embedded portion, and due to this difference in thermal expansion amount, the end portion of the heater and the tubular body are Stress is generated in the welded part.
If the welding strength between the end of the heater and the tubular body is not sufficient, the heater may be repeatedly turned on and off, and the end of the heater and the tubular body may come off.
Therefore, a technique for increasing the welding strength between the end portion of the heater and the tubular body has been proposed.
For example, in order to secure the welding strength between the heater and the inner cylinder, a method is proposed in which an annular support having a notch is provided on the outer wall of the inner cylinder, and one end of the heater protruding from the storage space is welded to the notch. Has been done.
However, during welding, the melting amount of the end portion of the heater having a smaller volume than that of the support becomes large. Therefore, the end of the heater may deteriorate, the end of the heater may become thin, or the welding between the support and the end of the heater may become insufficient, resulting in a decrease in the welding strength of the weld. is there. In this case, when the cross-sectional dimension (wire diameter) of the end portion of the heater is 1 mm or less, the welding strength of the welded portion is significantly reduced.
Therefore, further improvement has been desired with respect to the improvement of the welding strength of the welded portion.

JP, 2011-129384, A JP, 2016-058348, A

The problem to be solved by the present invention is to provide an impregnated-type cathode assembly capable of increasing the welding strength between the heater and the support.

The impregnated-type cathode assembly according to the embodiment includes a cathode substrate impregnated with an electron emitting material and having an electron emission surface, an outer cylinder provided on a surface of the cathode substrate opposite to the electron emission surface, and the external member. An inner cylinder provided inside the cylinder and an outer wall of an end of the inner cylinder opposite to the cathode base side, or an inner wall of an end of the outer cylinder opposite to the cathode base side. A ring-shaped support member having a cutout portion, a coil provided inside the cutout portion, and made of a spirally wound linear member, and the outer wall of the inner cylinder and the outer cylinder. The heater is provided between the inner wall and the inner wall, and one end of the heater is provided inside the coil. Inside the notch, the support and the coil, and the heater and the coil are fused and fixed.

FIG. 3 is a schematic partial cross-sectional view for illustrating the impregnated-type cathode assembly 1 according to the present embodiment. FIG. 6 is an enlarged schematic perspective view for illustrating the end portion 44 of the heater 40, the coil 70, and the welded portion 80 of the support body 30.

Embodiments will be exemplified below with reference to the drawings. In the drawings, the same components are designated by the same reference numerals, and detailed description thereof will be appropriately omitted.

The impregnated-type cathode assembly 1 according to the present embodiment can be, for example, a cathode assembly used in a klystron electron gun.
However, the application of the impregnated cathode structure 1 is not limited to the klystron.

FIG. 1 is a schematic partial sectional view for illustrating an impregnated-type cathode assembly 1 according to this embodiment.
As shown in FIG. 1, the impregnated cathode structure 1 includes a cathode substrate 10, a cylindrical body 20, a support 30, a heater 40, an embedded portion 50, a first reflector 60, a second reflector 62, a reflector 66, and Also, the coil 70 is provided.

The cathode substrate 10 is impregnated with an electron emitting substance. The cathode substrate 10 has an electron emission surface 12. The cathode substrate 10 can be formed of, for example, porous tungsten (W) having a porosity of about 20%. The cathode substrate 10 has, for example, a disc shape. The diameter dimension of the cathode substrate 10 can be about 50 mm. The cathode substrate 10 has an electron emission surface 12 having a predetermined curvature and recessed in a curved shape. The holes of the cathode substrate 10 are impregnated with an electron emitting substance made of, for example, barium oxide (BaO), calcium oxide (CaO), and aluminum oxide (Al ₂ O ₃ ).

In addition, the holes may be crushed when the electron emission surface 12 is processed. When the crushing occurs, the holes may not be sufficiently impregnated with the electron emitting substance. In order to prevent this, it is desirable that the holes of the cathode substrate 10 be impregnated with an electron emitting substance as follows.
First, before processing the electron emission surface 12, the holes in the cathode substrate 10 are impregnated with plastic. Next, after processing the electron emission surface 12, the cathode substrate 10 is heated in a hydrogen atmosphere or under vacuum to scatter the impregnated plastic.
After that, the holes of the cathode substrate 10 are impregnated with an electron emitting substance.
By doing so, the holes of the cathode substrate 10 can be sufficiently impregnated with the electron emitting substance.

The cylindrical body 20 supports the cathode substrate 10. The tubular body 20 also has a function of housing the heater 40 and the embedded portion 50 in the housing space 22 formed inside.
The cylindrical body 20 has an outer cylinder 24 and an inner cylinder 26.

The outer cylinder 24 and the inner cylinder 26 can be formed from molybdenum (Mo). The outer cylinder 24 and the inner cylinder 26 have a cylindrical shape. The outer cylinder 24 is provided on the surface of the cathode substrate 10 opposite to the electron emission surface 12. The inner cylinder 26 is arranged inside the outer cylinder 24 so as to be coaxial (concentric) with the outer cylinder 24. Therefore, an annular storage space 22 is formed between the outer wall of the inner cylinder 26 (wall surface on the outer cylinder 24 side) and the inner wall of the outer cylinder 24 (wall surface on the inner cylinder 26 side). For example, the inner cylinder 26 may have a diameter of about 15 mm, an axial length of about 15 mm, and a wall thickness of about 1 mm.

One end of the storage space 22 is closed by the cathode substrate 10. The cathode base 10 is joined to one end of the outer cylinder 24 and the inner cylinder 26. For example, one end of the outer cylinder 24 and the inner cylinder 26 and the back surface (the surface opposite to the electron emission surface 12) 14 of the cathode substrate 10 may be made of a ruthenium-molybdenum (Ru-Mo) alloy. It is attached.

The support 30 has an annular shape and is provided on the outer wall of the inner cylinder 26. The support 30 is provided near the end of the inner cylinder 26 on the side opposite to the cathode base 10 side. The support 30 is welded to the inner cylinder 26. The support 30 can be welded by, for example, arc welding. For example, the inner peripheral diameter of the support 30 can be about 15 mm, the outer peripheral diameter can be about 20 mm, and the thickness can be about 1 mm. However, the dimensions of the support 30 are not limited to those illustrated.

The support 30 has a cutout portion 31. The notch 31 penetrates the support 30 in the thickness direction. Inside the notch 31, the end 44 of the heater 40 and the coil 70 are provided. (See Figure 2)
For example, when the outer diameter of the coil 70 is 1.6 mm, the width of the notch 31 on the inner cylinder 26 side is about 1.6 mm before the end portion 44 and the coil 70 are provided. You can In this case, if the width dimension of the cutout portion 31 is made slightly smaller than the outer peripheral diameter dimension of the coil 70, the end portion 44 of the heater 40 and the coil 70 are held by the support body 30 by the elastic force. You can In addition, if the width dimension of the cutout portion 31 is set to be slightly larger than the outer peripheral diameter dimension of the coil 70, even if the end portion 44 of the heater 40 is inclined, the inside of the cutout portion 31 is reduced. It is easy to provide the end portion 44 of the heater 40 and the coil 70 in the.
It should be noted that the size of the cutout portion 31 is not limited to the illustrated size, and can be appropriately changed depending on the outer diameter size of the coil 70.

The end portion 44 of the heater 40, the coil 70, and the support body 30 are welded. Details of these weldings will be described later.

The heater 40 heats the cathode substrate 10 via an embedded portion 50 described later. The heater 40 is a filament made of a linear member. The linear member may be, for example, a tungsten (W) wire having a cross-sectional dimension (wire diameter) of 0.6 mm or a molybdenum (Mo) wire having a cross-sectional dimension (wire diameter) of 0.6 mm. An intermediate portion (heat generating portion) 42 of the heater 40 has a coil shape. The intermediate portion 42 is provided inside the embedded portion 50. The central axis of the intermediate portion 42 extends, for example, along the circumferential direction of the inner cylinder 26.

A coil 70, which will be described later, is provided at one end 44 of the heater 40. The end portion 44 of the heater 40 is electrically connected to the inner cylinder 26 via the coil 70 and the support body 30. That is, the heater 40, the cylindrical body 20, and the cathode substrate 10 have the same potential.

The other end 46 of the heater 40 extends to the outside of the impregnated cathode assembly 1 through an alumina tube 48. The end portion 46 of the heater 40 is electrically connected to a power supply device (not shown).
The alumina tube 48 is provided on the side of the cylindrical body 20 opposite to the side on which the cathode substrate 10 is provided. The alumina tube 48 is provided to prevent the end portion 46 from being broken near the surface of the embedded portion 50 and to insulate the heater 40 from the first reflection plate 60 and the heater 40 and the second reflection plate 62. ing.

The embedded portion 50 transfers the heat from the heater 40 to the cathode substrate 10. The embedded section 50 holds the heater 40 housed in the housing space 22. The embedded portion 50 insulates the heater 40. The embedded portion 50 is, for example, a sintered body of alumina (aluminum oxide), and is filled in the storage space 22 in which the intermediate portion 42 of the heater 40 is stored without any gap.

The first reflection plate 60, the second reflection plate 62, and the reflection cylinder 66 play a role of suppressing heat radiation from the storage space 22 to the outside and increasing heating efficiency of the cathode substrate 10 by radiation.

The first reflector 60 may be made of molybdenum (Mo). The first reflector 60 can be an annular plate-shaped body. The first reflection plate 60 is provided so as to close the opening of the storage space 22 on the side opposite to the side on which the cathode substrate 10 is provided. The first reflector 60 is welded to the outer cylinder 24 by arc welding.

The second reflection plate 62 has a disc shape and can be formed of molybdenum (Mo). The second reflector 62 is provided on the side of the first reflector 60 opposite to the outer cylinder 24 side. An annular spacer 64 is provided between the first reflector 60 and the second reflector 62. The spacer 64 and the first reflector 60 are welded by arc welding. The spacer 64 and the second reflector 62 are welded by arc welding.

The reflecting cylinder 66 can be formed using, for example, a thin plate of rhenium-molybdenum (Re-Mo) alloy. The reflecting cylinder 66 is arranged outside the outer cylinder 24 with a space therebetween. One end (the end portion on the cathode base 10 side) of the reflection cylinder 66 is brazed to the outer cylinder 24. Brazing can be performed using, for example, a ruthenium-molybdenum-nickel (Ru-Mo-Ni) alloy. An annular flange member 68 is brazed to the other end (the end opposite to the cathode base 10 side) of the reflecting cylinder 66. Brazing can be performed using, for example, a ruthenium-molybdenum-nickel alloy.
The impregnated cathode structure 1 is fixed to an electron gun section (not shown) via a flange member 68.

The coil 70 may be formed by spirally winding a linear member. There may be a gap between the linear members in the axial direction of the coil 70, but it is preferable that the linear members are in contact with each other. If the linear members are in contact with each other, the rigidity of the coil 70 can be increased, so that the welding described later becomes easy.
Further, considering the quality of the welded portion 80, the ease of welding, and the like, it is preferable that the cross-sectional dimension (wire diameter) of the linear member be smaller than the cross-sectional dimension (wire diameter) of the end portion 44 of the heater 40. ..

The linear member of the coil 70 is selected from the group consisting of tungsten (W), molybdenum (Mo), rhenium (Re), tantalum (Ta), niobium (Nb), platinum (Pt), and alloys thereof. At least one selected from the above can be included.
Considering the quality of the welded portion 80 and the ease of welding, it is preferable that the heater 40, the coil 70, and the support 30 are made of the same material.

According to the knowledge obtained by the present inventor, the cross-sectional dimension (wire diameter) of the linear member of the coil 70 is preferably 1/2 or less of the cross-sectional dimension (wire diameter) of the end portion 44 of the heater 40.
For example, the heater 40, the coil 70, and the support 30 are made of molybdenum (Mo), the end portion 44 of the heater 40 has a cross-sectional dimension (line diameter) of 0.6 mm, and the coil 70 has a cross-sectional dimension (line dimension). Diameter) can be 0.3 mm.

Further, it is preferable that the end of the coil 70 on the second reflection plate 62 side protrudes from the support 30. For example, it is preferable that the end of the coil 70 on the side of the second reflection plate 62 protrudes from the support 30 by the diameter dimension of the linear member or more.
By doing so, the quality of the welded portion 80, the workability of welding work, and the like can be improved.

The end of the coil 70 on the cathode substrate 10 side may or may not project from the support 30. In this case, if the end of the coil 70 on the cathode substrate 10 side reaches the embedded portion 50, the end 44 of the heater 40 can be protected. (See Figure 2)
Further, the outer peripheral surface of the coil 70 may or may not protrude from the outer peripheral surface of the support body 30. In this case, if the outer peripheral diameter of the support 30 is reduced, the outer peripheral surface of the coil 70 projects from the outer peripheral surface of the support 30. If the outer peripheral diameter of the support 30 is reduced, the support 30 can be easily melted during welding, so that the quality of the welded portion 80 and the workability of welding work can be improved.

Next, welding of the end portion 44 of the heater 40, the coil 70, and the support body 30 will be further described.
FIG. 2 is an enlarged schematic perspective view for illustrating the end portion 44 of the heater 40, the coil 70, and the welded portion 80 of the support body 30. Note that FIG. 2 is an enlarged perspective view of the portion A in FIG.

As shown in FIG. 2, the vicinity of the notch 31 of the support 30, the coil 70, and the end 44 of the heater 40 are welded. Furthermore, these and the inner cylinder 26 may be welded. The welded portion becomes the welded portion 80.

In the impregnated cathode structure 1 according to the present embodiment, the end portion 44 of the heater 40 and the coil 70 are provided inside the cutout portion 31 of the support body 30. Since the end portion 44 of the heater 40 and the coil 70 are sandwiched between the support bodies 30, the posture can be stabilized during welding.
Further, as described above, the cross-sectional dimension (wire diameter) of the linear member of the coil 70 is smaller than the cross-sectional dimension (wire diameter) of the end portion 44 of the heater 40. Therefore, during welding, the linear member of the coil 70 having a small volume is melted, and the end portion 44 of the heater 40, the support body 30, and the inner cylinder 26 can be closely joined.
Furthermore, since the linear member of the coil 70 having a small volume may be melted, the welding current can be reduced. Therefore, overmelting of the end portion 44 of the heater 40 can be suppressed. That is, the end portion 44 of the heater 40 may deteriorate, the end portion 44 of the heater 40 may become thin, and the welding between the support body 30 and the inner cylinder 26 and the end portion 44 of the heater 40 may become insufficient. Can be suppressed. As a result, it is possible to prevent the welding strength of the welded portion 80 from decreasing.

According to the impregnated cathode structure 1 according to the present embodiment, even when the heater 40 is repeatedly turned on and off, and when the heater 40 is rapidly heated, the end portion 44 of the heater 40 and the support body 30 are Can be hard to come off.
Further, it is possible to improve workability in welding work, improve quality of the welded portion 80, and improve reliability of the welded portion 80.

Next, a method for manufacturing the impregnated cathode structure 1 according to the present embodiment will be illustrated.
First, the tubular body 20 is placed on the back surface 14 of the cathode substrate 10 which is not impregnated with the electron emitting material, and the ruthenium-molybdenum alloy is applied to the joint portion between the cathode substrate 10 and the tubular body 20. Similarly, a ruthenium-molybdenum alloy is applied to the back surface 14 of the cathode substrate 10. After coating, the ruthenium-molybdenum alloy is melted, the cathode base 10 and the cylindrical body 20 are joined together, and a ruthenium-molybdenum alloy film is formed on the back surface 14 of the cathode base 10. This film of ruthenium-molybdenum alloy is provided in order to prevent the electron emitting material from seeping out from the back surface 14 of the cathode substrate 10 into the storage space 22 when the cathode emitting substrate 12 is impregnated with the electron emitting substance. It is provided.

Next, the heater 40 is held at a predetermined position in the storage space 22 by using a jig, and the storage space 22 is filled with the embedded portion 50. The embedding part 50 can be formed, for example, by pouring a paste-like material into the storage space 22 and then performing drying and sintering.
The pasty material can be produced, for example, by adding powdered alumina to an organic solvent containing a binder and stirring this.
Further, the drying is performed in order to scatter 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 support 30 is attached to the inner cylinder 26.
Next, the coil 70 is attached to the end portion 44 of the heater 40.
Next, the end 44 of the heater 40 to which the coil 70 is attached is provided inside the notch 31 of the support 30 so that the support 30 holds the coil 70 and the end 44 of the heater 40.
Next, with the end portion 44 of the heater 40 to which the coil 70 is attached being held by the support body 30, the coil 70 is welded to the vicinity of the cutout portion 31 of the support body 30.

Next, the support 30 and the inner cylinder 26 are welded.
Next, the first reflection plate 60 is welded to the tubular body 20, and the second reflection plate 62 is welded to the first reflection plate 60 via the spacer 64.
Next, one end of the reflection cylinder 66 (end on the cathode base 10 side) is installed outside the outer cylinder 24, and a ruthenium-molybdenum-nickel alloy is applied to the joint between the reflection cylinder 66 and the outer cylinder 24. Apply. Similarly, a flange member 68 is arranged at the other end (the end opposite to the cathode substrate 10 side) of the reflecting cylinder 66, and a ruthenium-molybdenum-nickel alloy is formed at the joint between the reflecting cylinder 66 and the flange member 68. Apply. After the application, the ruthenium-molybdenum-nickel alloy is melted and the reflecting cylinder 66, the outer cylinder 24 and the flange member 68 are joined.
Finally, the cathode substrate 10 is impregnated with an electron emitting substance, and the impregnated cathode assembly 1 is completed.

Impregnation with the electron emitting substance can be performed as follows.
First, an electron emitting substance is placed on the electron emitting surface 12 of the cathode substrate 10.
Next, the electron emitting substance is heated to about 1600° C. in a hydrogen atmosphere. Then, the electron emitting substance melts and impregnates the cathode substrate 10.

In the above, the support body 30 having the cutout portion 31 is provided on the outer wall of the end portion of the inner cylinder 26 (the wall surface on the outer cylinder 24 side), and the heater 40 in which the coil 70 is attached is provided inside the cutout portion 31. The case where the one end 44 is provided has been described.
However, the support body 30 having the cutout portion 31 is provided on the inner wall of the end portion of the outer cylinder 24 (the wall surface on the inner cylinder 26 side), and inside the cutout portion 31, one of the heaters 40 having the coil 70 attached thereto is provided. Even if the end portion 44 is provided, the same effect can be obtained.
That is, the support 30 having the notch 31 is the outer wall of the end of the inner cylinder 26 opposite to the cathode base 10 side or the inner wall of the end of the outer cylinder 24 opposite the cathode base 10 side. Can be provided.

Although some embodiments of the present invention have been illustrated above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and its equivalent scope. Further, the above-described respective embodiments can be implemented in combination with each other.

DESCRIPTION OF SYMBOLS 1 Impregnation type cathode structure, 10 Cathode base, 12 Electron emission surface, 20 Cylindrical body, 22 Storage space, 24 Outer cylinder, 26 Inner cylinder, 30 Support body, 31 Notch part, 40 Heater, 44 End part, 50 Embedded part , 60 first reflector, 62 second reflector, 66 reflector, 70 coil, 80 weld

Claims (5)

A cathode substrate impregnated with an electron emitting material and having an electron emitting surface;
An outer cylinder provided on the surface of the cathode base opposite to the electron emission surface,
An inner cylinder provided inside the outer cylinder,
It is provided on the outer wall of the end of the inner cylinder opposite to the side of the cathode base or on the inner wall of the end of the outer cylinder on the side opposite to the side of the cathode base, and has an annular shape and has a notch. A support,
A coil that is provided inside the cutout portion and that includes a linear member that is spirally wound,
A heater provided between the outer wall of the inner cylinder and the inner wall of the outer cylinder, and one end of which is provided inside the coil;
Equipped with
An impregnated-type cathode assembly in which the support and the coil, and the heater and the coil are melted and fixed inside the cutout portion . The impregnated-type cathode assembly according to claim 1, wherein a cross-sectional dimension of the linear member of the coil is smaller than a cross-sectional dimension of the one end of the heater. The impregnated-type cathode assembly according to claim 1 or 2, wherein the linear members of the coil are in contact with each other. The linear member of the coil includes at least one selected from the group consisting of tungsten, molybdenum, rhenium, tantalum, niobium, platinum, and alloys thereof. The impregnated-type cathode assembly according to [4]. The impregnated cathode assembly according to claim 1, wherein the support, the coil, and the heater are welded together.