JP2011129361A - Impregnated cathode structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make jointing of a heater and a support less apt to separate, in an impregnated cathode structure. <P>SOLUTION: The impregnated cathode structure 1 includes a cathode substrate 10 in which an electron emitting substance is impregnated, a support 20, a heater 40 and an embedded material 50. The support 20 has a support outer cylinder 24 and a support inner cylinder 26, arranged coaxially with the support outer cylinder 24 in the cylinder of the support outer cylinder 24 so as to form a housing space 22 of a ring shape between the support outer cylinder 24. The cathode substrate 10 is installed on and supported by the support 20. The heater 40 is partially housed in the housing space 22 and one of the end part 44 is electrically connected to the support 20. Recessed portions 24a, 26a, extending respectively in the axial direction, are formed at the inner circumference of the support outer cylinder 24 and the outer circumference of the support inner cylinder 26. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an impregnated cathode assembly used for an electron gun of a microwave electron tube such as a klystron or a gyrotron.

  Currently, for example, microwave electron tubes such as klystrons used in nuclear fusion and particle accelerators have reached the megawatt class, and higher output is desired. Therefore, in such a high-power microwave electron tube, an electron gun using an impregnated cathode is used instead of the oxide cathode (see, for example, Patent Document 1 and Patent Document 2).

  The structure of the impregnated cathode assembly 101 will be described with reference to FIG. FIG. 10 is a partial longitudinal sectional view of an impregnated cathode assembly.

  The impregnated cathode assembly 101 is a cathode assembly used for an electron gun of a klystron, and includes a cathode substrate 110, a support 120, a heater 140, a filling material 150, and the like.

  The cathode substrate 110 is made of porous tungsten (W) and is formed into a disk shape. The cathode substrate 110 is formed with an electron emission surface 112 that is recessed in a curved shape. The holes of the cathode substrate 110 are impregnated with an electron emitting substance.

  In addition to supporting the cathode substrate 110, the support 120 plays a role of storing the heater 140 and the embedding material 150 in a storage space 122 formed therein. The support 120 has a cylindrical support outer cylinder 124 and a support inner cylinder 126 made of molybdenum (Mo). The support inner cylinder 126 is disposed coaxially (concentrically) with the support outer cylinder 124 in the cylinder of the support outer cylinder 124 so that an annular storage space 122 is formed between the support inner cylinder 124 and the support outer cylinder 124.

  The cathode substrate 110 is brazed to one end of the support outer cylinder 124 and the support inner cylinder 126 using a ruthenium-molybdenum (Ru-Mo) alloy.

  The heater 140 plays a role of heating the cathode substrate 110 through an embedding material 150 described later. The heater 140 is a tungsten (W) wire wound in a coil shape, and is stored in the storage space 122. One end 144 of the heater 140 is joined to the outer wall of the support inner cylinder 126, and the heater 140 and the cathode base 110 have the same potential.

  The embedding material 150 plays a role of holding the heater 140 stored in the storage space 122 in addition to transferring the heat from the heater 140 to the cathode base 110. The embedding material 150 is, for example, an alumina sintered body, and the storage space 122 in which the heater 140 is stored is filled without a gap.

Japanese Patent Laid-Open No. 2001-256883 JP-A-2-253538

  In the above-described impregnated-type cathode assembly 101, for example, the embedded material 150 made of alumina or the like has a higher coefficient of thermal expansion than the support 120 made of a metal such as molybdenum (Mo). May be expanded by heating, and may move in the circumferential direction in the storage space 122. As a result, stress is applied to the joint portion between the one end 144 of the heater 140 and the outer wall of the support inner cylinder 126. When the heater 140 is repeatedly turned on and off, the heater 140 and the support inner cylinder 126 may be disconnected from each other.

  In particular, when the one end 144 of the heater 140 and the outer wall of the support inner cylinder 126 are brazed with a brazing material having a high melting temperature, for example, the one end 144 of the heater 140 made of tungsten wire is recrystallized to reheat the heater. One end 144 of 140 is fragile. For this reason, the stress applied to the joining portion makes the one end 144 of the heater 140 and the outer wall of the supporting inner cylinder 126 easily come off.

  Therefore, the present invention has been made to solve the above-described problems, and an object thereof is to make it difficult to disconnect the heater and the support.

  In order to achieve the above object, an impregnated-type cathode assembly according to the present invention includes a cathode base impregnated with an electron-emitting material, and a cylindrical support outer cylinder in which a storage space is formed in the cylinder, A support body to which the cathode base body is attached and which supports the cathode base body, is formed in a linear shape, and at least a part is housed in the housing space of the support body, and one end portion is joined to the support body. And a concave portion or a convex portion extending in the circumferential direction is formed on the wall surface forming the storage space of the support. It is characterized by being.

  According to the present invention, it is possible to make it difficult to disconnect the heater and the support.

It is a fragmentary longitudinal cross-sectional view of the impregnated-type cathode assembly according to the first embodiment and the second embodiment of the present invention. It is a figure for demonstrating the impregnation-type cathode structure which concerns on the 1st Embodiment of this invention, Comprising: It is a perspective view of a support outer cylinder. It is a figure for demonstrating the impregnation-type cathode structure which concerns on the 1st Embodiment of this invention, Comprising: It is a perspective view of a support inner cylinder. It is a figure for demonstrating the impregnation-type cathode structure which concerns on the 2nd Embodiment of this invention, Comprising: It is a perspective view of a support outer cylinder. It is a figure for demonstrating the impregnation-type cathode structure which concerns on the 2nd Embodiment of this invention, Comprising: It is a perspective view of a support inner cylinder. It is a fragmentary longitudinal cross-sectional view of the impregnation-type cathode structure which concerns on the 3rd Embodiment of this invention. It is a figure for demonstrating the impregnation-type cathode structure which concerns on the 3rd Embodiment of this invention, Comprising: It is a perspective view of a support body. It is a fragmentary longitudinal cross-sectional view of the impregnation-type cathode assembly which concerns on the 4th Embodiment of this invention. It is a figure for demonstrating the impregnation-type cathode structure which concerns on the 4th Embodiment of this invention, Comprising: It is a perspective view of a support body (support outer cylinder). It is a partial longitudinal cross-sectional view of a conventional impregnated-type cathode assembly.

[First Embodiment]
A first embodiment of an impregnated cathode assembly according to the present invention will be described with reference to FIGS. The impregnated-type cathode assembly 1 according to this embodiment is a cathode assembly used for an electron gun of a klystron.

  First, the structure of the impregnated cathode assembly 1 according to the present embodiment will be described with reference to FIG. FIG. 1 is a partial longitudinal sectional view of an impregnated-type cathode assembly according to this embodiment.

  The impregnated cathode assembly 1 includes a cathode substrate 10, a support 20, a heater 40, a filling material 50, reflectors 60 and 62, a reflector cylinder 66, and the like.

The cathode substrate 10 is made of, for example, porous tungsten (W) having a porosity of 15 to 20%, and is formed into a disk shape having a diameter of 70 mm, for example. The cathode substrate 10 is formed with an electron emission surface 12 that is recessed into a curved surface with a predetermined curvature. The holes of the cathode base 10 are impregnated with an electron emitting material made of, for example, barium oxide (BaO), calcium oxide (CaO), and aluminum oxide (Al ₂ O ₃ ).

  In addition, when the electron emission surface 12 is processed, the pores are easily crushed, and the electron emission material may not be sufficiently impregnated in the cavities due to the crushing. In order to prevent this, the holes of the cathode base 10 are impregnated with plastic before the electron emission surface 12 is processed, and after the electron emission surface 12 is processed, the cathode base 10 is heated in a hydrogen atmosphere or under vacuum, It is desirable to scatter the impregnated plastics and then impregnate the holes of the cathode substrate 10 with the electron emitting material.

  In addition to supporting the cathode substrate 10, the support 20 plays a role of storing the heater 40 and the embedding material 50 in the storage space 22 formed inside. The support 20 has a support outer cylinder 24 and a support inner cylinder 26.

  The support outer cylinder 24 and the support inner cylinder 26 are each made of molybdenum (Mo) and are formed into a cylindrical shape. The support inner cylinder 26 is disposed coaxially (concentrically) with the support outer cylinder 24 in the cylinder of the support outer cylinder 24 so that an annular storage space 22 is formed between the support outer cylinder 24 and the support outer cylinder 24. The support inner cylinder 26 is molded to have a diameter of 20 mm, an axial length of 15 mm, and a plate thickness of 2 mm, for example.

  The cathode base 10 is disposed so as to close one end of the storage space 22, and is joined to one end of the support outer cylinder 24 and the support inner cylinder 26. Specifically, one end of the support outer cylinder 24 and the support inner cylinder 26 and the back surface (surface opposite to the electron emission surface 12) 14 of the cathode base 10 are, for example, ruthenium-molybdenum (Ru-Mo). It is brazed using an alloy.

  The heater 40 plays a role of heating the cathode substrate 10 through an embedding material 50 described later. The heater 40 is a filament formed in a linear shape, for example, a tungsten (W) wire having a diameter of 1.5 mm. An intermediate portion (heat generation portion) 42 of the heater 40 is wound in a coil shape and stored in the storage space 22. In addition, the winding axis | shaft of the heater 40 is extended in the circumferential direction of the support body 20, for example.

  One end 44 of the heater 40 is electrically connected to the support 20. For example, one end 44 of the heater 40 is brazed to the outer peripheral surface of the support inner cylinder 26 using a Ru—Mo alloy. Therefore, the heater 40, the support 20 and the cathode base 10 are at the same potential.

  On the other hand, the other end portion 46 of the heater 40 extends through the alumina tube 48 provided at the end portion of the support 20 away from the cathode base 10 and extends to the outside of the impregnated cathode assembly 1, and is not shown. It is connected to the. The alumina tube 48 is provided to prevent the heater 40 from breaking near the surface of the embedding material 50 described later and to insulate the heater 40 from the first reflector 60 described later.

  The embedding material 50 plays a role of holding the heater 40 stored in the storage space 22 in addition to transferring the heat from the heater 40 to the cathode base 10. The embedding material 50 is, for example, an alumina sintered body, and fills the storage space 22 in which the intermediate portion (heat generation portion) 42 of the heater 40 is stored without a gap.

  The first reflecting plate 60, the second reflecting plate 62, and the reflecting cylinder 66 serve to suppress heat radiation from the storage space 22 to the outside and increase the heating efficiency of the cathode substrate 10 by radiation.

  The first reflecting plate 60 is an annular plate body made of molybdenum (Mo), and is disposed so as to close the opening away from the cathode base 10 in the storage space 22. The outer edge of the first reflector 60 is joined to the end of the support outer cylinder 24 by arc welding, and the inner edge of the first reflector 60 is joined to the end of the support inner cylinder 26 by arc welding. Yes.

  The second reflector 62 is a disc made of molybdenum (Mo), and is disposed outside the first reflector 60 and joined to the first reflector 60 by arc welding via an annular spacer 64. Has been.

  Further, the reflection cylinder 66 is made of a thin plate of rhenium-molybdenum (Re-Mo) alloy, and is disposed on the outer periphery of the support outer cylinder 24 at a distance from the support outer cylinder 24. One end of the reflecting tube 66 (the end near the cathode base 10) is brazed to the support outer tube 24 using a ruthenium-molybdenum-nickel (Ru-Mo-Ni) alloy. An annular flange member 68 is brazed using a Ru—Mo—Ni alloy to the other end of the reflecting tube 66 (an end portion away from the cathode substrate 10). The impregnated-type cathode assembly 1 is fixed to an electron gun portion (not shown) via the flange member 68.

  Next, the structure of the characteristic part of the impregnated-type cathode assembly 1 according to this embodiment will be described with reference to FIGS. FIG. 2 is a perspective view of the support outer cylinder, and FIG. 3 is a perspective view of the support inner cylinder.

  Concave portions 24 a and 26 a intersecting with the circumferential direction of the storage space 22 are formed on the wall surface (for example, the inner peripheral surface of the support outer cylinder 24 and the outer peripheral surface of the support inner cylinder 26) forming the storage space 22 of the support 20. Is formed.

  Specifically, as shown in FIG. 2, six recesses 24 a extending in the axial direction of the support outer cylinder 24 are formed on the inner peripheral surface of the support outer cylinder 24 at equal intervals in the circumferential direction. Further, as shown in FIG. 3, six concave portions 26 a extending in the axial direction of the support inner cylinder 26 are formed on the outer peripheral surface of the support inner cylinder 26 at equal intervals in the circumferential direction. Note that it is desirable that three or more recesses 24a and 26a are formed.

  A method for manufacturing the impregnated-type cathode assembly 1 according to the present embodiment will be described. The impregnated-type cathode assembly 1 is manufactured as follows, for example.

  First, the support 20 is placed on the back surface of the cathode base 10 that is not impregnated with the electron emitting substance, and a Ru—Mo alloy is applied to the joint portion between the cathode base 10 and the support 20. Further, the heater 40 is held at a predetermined position in the storage space 22 by a jig, and a Ru—Mo alloy is applied to a joint portion between the end portion 44 of the heater 40 and the support inner cylinder 26. At the same time, a Ru—Mo alloy is applied to the back surface 14 of the cathode substrate 10. After the application, the Ru—Mo alloy is dissolved, the cathode base 10 and the support 20 are joined, and a Ru—Mo alloy film is formed on the back surface 14 of the cathode base 10. This Ru—Mo alloy film prevents the electron emitting material from oozing out from the back surface 14 of the cathode substrate 10 into the storage space 22 when the electron emitting material 12 is impregnated from the electron emitting surface 12 of the cathode substrate 10. Is.

  Thereafter, the embedding material 50 is filled in the storage space 22. The filling material 50 is filled, for example, by adding powdered alumina to an organic solvent containing a binder and stirring to make a paste, and then pouring it into the storage space 22, and then the organic solvent is scattered by drying. Sintering is performed at 1750 to 1850 ° C. in a vacuum or in a hydrogen atmosphere.

  After the filling material 50 is filled, the first reflecting plate 60 is welded to the support 20, and the second reflecting plate 62 is welded to the first reflecting plate 60 via the spacer 64. Further, the reflecting cylinder 66 is brazed to the support 20.

  Finally, an electron emitting material is placed on the electron emitting surface 12 of the cathode substrate 10, the electron emitting material is melted at 1600 to 1700 ° C. in a hydrogen atmosphere, and impregnated in the cathode substrate 10. Complete.

  The effects of the impregnated cathode assembly 1 according to this embodiment will be described.

  According to the present embodiment, the wall surface forming the storage space 22 is formed with the recesses 24a and 26a intersecting with the circumferential direction. That is, a plurality of concave portions 24 a and 26 a extending in the axial direction are formed on the inner peripheral surface of the support outer cylinder 24 and the outer peripheral surface of the support inner cylinder 26. Therefore, when the heater 40 is heated, the embedding material 50 made of alumina hardly moves in the circumferential direction in the storage space 22. As a result, even if the heater 40 is repeatedly turned on and off, the connection between the heater 40 and the support inner cylinder 26 is unlikely to come off, and a current can be stably supplied to the heater 40.

[Second Embodiment]
A second embodiment of an impregnated cathode assembly according to the present invention will be described with reference to FIGS. 1, 4 and 5. FIG. FIG. 1 is a partial longitudinal sectional view of an impregnated-type cathode assembly according to this embodiment. FIG. 4 is a perspective view of the support outer cylinder, and FIG. 5 is a perspective view of the support inner cylinder. In addition, since this embodiment is a modification of 1st Embodiment, the same code | symbol is attached | subjected to an overlapping part and description of the structure of the part is abbreviate | omitted.

  The basic structure of the impregnated-type cathode assembly 1 according to this embodiment is the same as that of the first embodiment.

  In the present embodiment, the wall surface (for example, the inner peripheral surface of the support outer cylinder 24 and the outer peripheral surface of the support inner cylinder 26) that forms the storage space 22 of the support 20 is arranged with respect to the circumferential direction of the storage space 22. Intersecting convex portions 24b and 26b are formed.

  Specifically, as shown in FIG. 4, six convex portions 24 b extending in the axial direction of the support outer cylinder 24 are formed on the inner peripheral surface of the support outer cylinder 24 at equal intervals in the circumferential direction. Further, as shown in FIG. 5, six convex portions 26 b extending in the axial direction of the support inner cylinder 26 are formed on the outer peripheral surface of the support inner cylinder 26 at equal intervals in the circumferential direction.

  Also according to this embodiment, the same effect as that of the first embodiment can be obtained. The same effect can be obtained even if both the concave portions 24a and 26a and the convex portions 24b and 26b are formed on the inner peripheral surface of the support outer cylinder 24 and the outer peripheral surface of the support inner cylinder 26.

[Third Embodiment]
A third embodiment of the impregnated cathode assembly according to the present invention will be described with reference to FIGS. In addition, since this embodiment is a modification of 1st Embodiment, the same code | symbol is attached | subjected to an overlapping part and description of the structure of the part is abbreviate | omitted.

  First, the structure of the impregnated cathode assembly 1 according to the present embodiment will be described with reference to FIG. FIG. 6 is a partial longitudinal sectional view of the impregnated-type cathode assembly according to this embodiment.

  The impregnated-type cathode assembly 1 according to this embodiment is a cathode assembly used for an electron gun of a gyrotron. The impregnated cathode assembly 1 includes a cathode substrate 10, a support 20, a heater 40, a filling material 50, a reflection plate 60, a reflection cylinder 66, and the like.

  The support 20 has a support outer cylinder 24, a support inner cylinder 26, and a closing plate 28. The support inner cylinder 26 is disposed coaxially (concentrically) with the support outer cylinder 24 in the cylinder of the support outer cylinder 24 so that an annular storage space 22 is formed between the support outer cylinder 24 and the support outer cylinder 24.

  The closing plate 28 is disposed so as to block one open end of the support 20 (one end of the support outer cylinder 24 and the support inner cylinder 26), and forms one end face of the storage space 22. The support outer cylinder 24, the support inner cylinder 26, and the closing plate 28 are integrally molded.

  The cathode substrate 10 is molded into a ring shape having an inner diameter of 80 mm and an outer diameter of 95 mm. The cathode substrate 10 is brazed to a flange portion 25 formed on the outer periphery of the support outer cylinder 24.

  The storage space 22 of the support 20 stores the heater 40 and is filled with the embedding material 50 as in the first embodiment.

  Here, the structure of the characteristic part of the impregnated-type cathode assembly 1 according to the present embodiment will be described with reference to FIG. FIG. 7 is a perspective view of the support.

  On the wall surface forming the storage space 22 of the support 20, a recess 28 a that intersects the circumferential direction of the storage space 22 is formed. Specifically, as shown in FIG. 7, a plurality of recesses 28 a extending radially in the radial direction are formed on the surface of the closing plate 28 on the storage space 22 side.

  Instead of the plurality of recesses 28a, there may be a plurality of projections, or both the recesses 28a and the projections may be formed.

  Also according to this embodiment, when the heater 40 is heated, the embedding material 50 hardly moves in the circumferential direction in the storage space 22, and the connection between the heater 40 and the support inner cylinder 26 is difficult to come off.

[Fourth Embodiment]
A fourth embodiment of the impregnated cathode assembly according to the present invention will be described with reference to FIG. FIG. 8 is a partial longitudinal sectional view of the impregnated cathode assembly according to the present embodiment. In addition, since this embodiment is a modification of 1st Embodiment, the same code | symbol is attached | subjected to an overlapping part and description of the structure of the part is abbreviate | omitted.

  The impregnated-type cathode assembly 1 according to the present embodiment is a general cathode assembly used for, for example, an electron gun of a traveling wave tube. The impregnated cathode assembly 1 includes a cathode substrate 10, a support 20, a heater 40, a filling material 50, a reflection plate 60, and the like.

  The support 20 is composed of a support outer cylinder 24, and a storage space 22 is formed inside the support outer cylinder 24. The cathode substrate 10 is disposed so as to block one opening end of the support outer cylinder 24, and the reflection plate 60 is disposed so as to block the other opening end of the support outer cylinder 24.

  Similar to the first embodiment, the wall surface forming the storage space 22 of the support body 20 is formed with a recess extending so as to intersect the circumferential direction. Specifically, six concave portions extending in the axial direction of the support outer cylinder 24 are formed on the inner peripheral surface of the support outer cylinder 24 at equal intervals in the circumferential direction.

  Also according to this embodiment, when the heater 40 is heated, the embedding material 50 made of alumina is difficult to move in the circumferential direction in the storage space 22, and the heater 40 and the support inner cylinder 26 are not easily disconnected.

[Other Embodiments]
The first embodiment and the second embodiment are merely examples, and the present invention is not limited to these.

  For example, in the first embodiment, the recesses 24 a and 26 a are formed on both the inner peripheral surface of the support outer cylinder 24 and the outer peripheral surface of the support inner cylinder 26, but only the inner peripheral surface of the support outer cylinder 24. Alternatively, it may be formed only on the outer peripheral surface of the support inner cylinder 26.

  Further, in the third embodiment, as in the first embodiment or the second embodiment, the inner peripheral surface of the support outer cylinder 24 and the outer peripheral surface of the support inner cylinder 26 are recessed portions 24a, 26a or convex portions 24b, 26b may be formed.

  Further, in the first embodiment, a concave portion or a convex portion extending radially in the radial direction may be formed on the surface of the reflector 60 facing the cathode base 10.

  Furthermore, in the first embodiment, the one end 40 of the heater 40 is joined to the inner peripheral surface of the support inner cylinder 26, but may be joined to the support outer cylinder 24 or the like.

DESCRIPTION OF SYMBOLS 1 ... Impregnation type | mold cathode structure, 10 ... Cathode base | substrate, 12 ... Electron emission surface of a cathode base | substrate, 14 ... Back surface of a cathode base | substrate, 20 ... Support body, 22 ... Storage space, 24 ... Support outer cylinder, 24a ... Support outer cylinder Concave part, 24b ... convex part of supporting outer cylinder, 25 ... flange part of supporting outer cylinder, 26 ... supporting inner cylinder, 26a ... concave part of supporting inner cylinder, 26b ... convex part of supporting inner cylinder, 28 ... blocking plate, 28a ... Blocking plate recess, 40 ... heater, 42 ... heater heating portion, 44, 46 ... heater end, 48 ... alumina tube, 50 ... embedding material, 60 ... first reflector, 62 ... second reflector, 64 ... Spacer, 66 ... Reflective tube, 68 ... Flange member

Claims (8)

A cathode substrate impregnated with an electron emitting material;
A cylindrical support outer cylinder in which a storage space is formed in a cylinder, and a support body to which the cathode substrate is attached to support the cathode substrate;
A heater formed linearly, at least a part of which is stored in the storage space of the support, and one end of which is joined to the support;
An insulating material filled in the storage space of the support;
An impregnated cathode assembly comprising:
An impregnated-type cathode assembly, wherein a concave portion or a convex portion extending so as to intersect the circumferential direction is formed on a wall surface forming the storage space of the support.   The impregnated-type cathode assembly according to claim 1, wherein the concave portion or the convex portion extending in the axial direction is formed on an inner peripheral surface of the support outer cylinder.   The impregnated-type cathode assembly according to claim 2, wherein three or more of the concave portions or the convex portions are formed on an inner peripheral surface of the support outer cylinder.   The support has a cylindrical support inner cylinder arranged coaxially with the support outer cylinder in the cylinder of the support outer cylinder so as to form an annular storage space between the support outer cylinder and the support outer cylinder. The impregnated-type cathode assembly according to any one of claims 1 to 3, wherein the concave portion or the convex portion extending in the axial direction is formed on an outer peripheral surface of the supporting inner cylinder.   The impregnated-type cathode assembly according to claim 4, wherein three or more of the concave portions or the convex portions are formed on an outer peripheral surface of the supporting inner cylinder.   The support has a closing plate that closes one end of the support outer cylinder to form one end surface of the storage space, and extends radially toward the surface of the storage space on the storage space side. The impregnated-type cathode assembly according to any one of claims 1 to 5, wherein a concave portion or the convex portion is formed.   6. The impregnated-type cathode assembly according to claim 4, wherein one end of the heater is joined to an inner wall of the support inner cylinder.   A reflecting plate for closing an end of the supporting outer cylinder opposite to the end to which the cathode substrate is mounted; and a radial extension to a surface of the reflecting plate facing the cathode substrate in a radial direction The impregnated-type cathode assembly according to any one of claims 1 to 5, wherein the concave portion or the convex portion is formed.

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