JP5398510B2 - Impregnated cathode structure - Google Patents

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).

  The structure of the impregnated cathode assembly 101 will be described with reference to FIG. FIG. 5 is a partial longitudinal sectional view of the 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 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 brazing material of 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 an alumina sintered body and fills the storage space 122 in which the heater 140 is stored without any gap.

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

  In the above-described impregnated-type cathode assembly 101, the support 120 and the embedding material 150 have different coefficients of thermal expansion. Therefore, the heating of the heater 140 causes a difference in thermal expansion between the support 120 and the embedding material 150. 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.

  Here, it is difficult to arrange the heater 140 at a predetermined position in the storage space 122 with sufficient accuracy, and when the contact area between the one end 144 of the heater 140 and the outer wall of the support inner cylinder 126 becomes small, The bonding strength cannot be secured. In this case, the heater 140 and the support inner cylinder 126 may be disconnected due to repeated turning on and off of the heater 140.

  Therefore, in order to secure the bonding strength (contact area) between the heater 140 and the support inner cylinder 126, a method is proposed in which a recess is formed in the outer wall of the support inner cylinder 126 and one end 144 of the heater 140 is welded to the recess. (See Patent Document 2). However, in order to weld the one end 144 of the heater 140 to the support inner cylinder 126 having a large heat capacity, it is necessary to perform heating for a long time with a high current, and the one end 144 of the heater 140 may be recrystallized and become brittle.

  The present invention has been made to solve the above-described problems, and an object thereof is to increase the bonding strength between a heater and a support.

  In order to achieve the above object, an impregnated cathode assembly according to the present invention forms an annular storage space between a cathode base impregnated with an electron emitting material, a support outer cylinder, and the support outer cylinder. The support outer cylinder has a support inner cylinder disposed coaxially with the support outer cylinder, and the cathode base is attached to support the cathode base, and A support formed with a protrusion protruding from the end surface, and formed in a linear shape, at least a part of which is stored in the storage space of the support, and one end is outside the storage space of the support A heater joined to the protrusion and an embedding material filled in a storage space of the support are provided.

  According to the present invention, the bonding strength between the heater and the support can be increased.

1 is a partial vertical cross-sectional view of an impregnated cathode assembly according to a first embodiment of the present invention. It is the perspective view which expanded the protrusion part vicinity of FIG. It is a fragmentary longitudinal cross-sectional view of the impregnation-type cathode structure which concerns on the 2nd Embodiment of this invention. It is the perspective view which expanded the protrusion part vicinity of FIG. 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 vertical cross-sectional view of an impregnated cathode assembly according to a first embodiment of the present invention.

  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 brazing material .

  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 inner cylinder 26. 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 substrate 10) is brazed to the support outer tube 24 using a ruthenium-molybdenum-nickel (Ru-Mo-Ni) alloy brazing material . An annular flange member 68 is brazed using a brazing material of 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 the present embodiment will be described with reference to FIG. FIG. 2 is an enlarged perspective view of the vicinity of the protrusion of FIG.

  A protruding portion 30 protruding from the end surface of the supporting inner cylinder 26 in the axial direction of the supporting inner cylinder 26 is formed at the end of the supporting inner cylinder 26 away from the cathode base 10. The protrusion 30 is formed integrally with the support inner cylinder 26. A through hole 61 is formed at a position corresponding to the protruding portion 30 of the first reflecting plate 60, and the protruding portion 30 is inserted through the through hole 61. In addition, the protrusion part 30 is formed in the square of the length of one side of a protrusion direction, for example, and the cross section of a protrusion direction is 1.5 mm on one side.

  Further, an end portion 44 of the heater 40 (an end portion opposite to the end portion 46 connected to the power supply device) 44 is inserted through a notch 61 formed in the inner edge portion of the first reflecting plate 60 to fill the filling material. 50 extends outside and is joined to the protrusion 30 outside the storage space 22. In the present embodiment, the end portion 44 of the heater 40 and the protruding portion 30 are joined by, for example, arc welding. In order to increase the bonding strength, the end portion 44 of the heater 40 extends in the protruding direction of the protruding portion 30, and the outer periphery of the end portion 44 of the heater 40 is bonded to one side surface of the rectangular parallelepiped protruding portion 30. .

  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 brazing material of Ru—Mo alloy is applied to the joint portion between the cathode base 10 and the support 20. At the same time, a Ru—Mo alloy brazing material is applied to the back surface 14 of the cathode substrate 10. After the application, the Ru—Mo alloy brazing material is melted , 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 heater 40 is held at a predetermined position in the storage space 22 with a jig, and the storage space 22 is filled with the filling material 50. 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 tube 66 is brazed to the support 20. Further, the end portion 44 of the heater 40 is welded to the protruding portion 30.

  Finally, an electron emitting material is placed on the electron emitting surface 12 of the cathode substrate 10, and 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 this embodiment, the end portion 44 (the end portion opposite to the end portion 46 connected to the power supply device) 44 of the heater 40 extends outside the embedding material 50 and is supported outside the storage space 22. It is joined to the protrusion 30 formed in the cylinder 26. Therefore, this joining portion is not easily subjected to stress due to a difference in thermal expansion generated between the support inner cylinder 26 and the embedding material 50 during heating, and even if the heater 40 is repeatedly turned on and off, the heater 40 and the support inner cylinder 26 Is difficult to come off. Therefore, the bonding strength between the heater 40 and the support 20 can be increased, and a current can be stably supplied to the heater 40.

  Further, in the conventional impregnated-type cathode assembly 101, one end 144 of the heater 140 is joined to the outer wall of the supporting inner cylinder 126 having a large heat capacity. 40 end portions 44 are joined. Therefore, in this embodiment, the heating amount (welding current) and the heating time at the time of welding can be reduced and the embrittlement of the heater 40 can be suppressed compared to the conventional case.

  Furthermore, according to the present embodiment, the end portion 44 of the heater 40 is joined to the protruding portion 30 formed on the support inner cylinder 26 outside the storage space 22. Therefore, the joining work between the end portion 44 of the heater 40 and the protruding portion 30 is facilitated, the contact failure between the heater 40 and the support 20 can be reduced, and the manufacturing cost can be reduced.

[Second Embodiment]
A second embodiment of the impregnated cathode assembly according to the present invention will be described with reference to FIGS. FIG. 3 is a partial vertical cross-sectional view of an impregnated cathode assembly according to the second embodiment of the present invention. 4 is an enlarged perspective view of the vicinity of the protruding portion in FIG. 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 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). 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.

  Next, the structure of the characteristic part of the impregnated-type cathode assembly 1 according to this embodiment will be described with reference to FIG.

  At the end portion of the support inner cylinder 26, a protruding portion 30 that protrudes from the end surface of the support inner cylinder 26 in the axial direction of the support inner cylinder 26 is formed. Further, the end portion 44 of the heater 40 is inserted through a notch 61 formed in the inner edge portion of the first reflecting plate 60, extends to the outside of the embedding material 50, and is joined to the protruding portion 30 outside the storage space 22. Has been.

  In the present embodiment, the distal end surface of the end portion 44 of the heater 40 and the distal end surface of the protruding portion 30 form approximately the same plane. Then, for example, 20 platinum ribbons 32 having a length of 3 mm, a width of 1 mm, and a thickness of 50 μm are stacked and placed on the front end surface of the end portion 44 of the heater 40 and the front end surface of the protruding portion 30. The end portion 44 of the heater 40 and the protruding portion 30 are electrically connected by melting the ribbon 32.

  Also according to this embodiment, the same effect as that of the first embodiment can be obtained.

[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 related to the impregnated-type cathode assembly 1 for klystrons, the end portion 44 of the heater 40 and the protruding portion 30 are joined by arc welding, but as described in the second embodiment. In addition, the platinum ribbon 32 may be dissolved to be joined. Conversely, in the second embodiment of the impregnated cathode assembly 1 for gyrotron, the end portion 44 of the heater 40 and the protruding portion 30 are joined by dissolving the platinum ribbon 32. As described in the embodiment, they may be joined by arc welding.

  Moreover, the protrusion 30 does not need to be molded integrally with the support inner cylinder 26, and may be joined to one end surface of the support inner cylinder 26 by, for example, brazing. Furthermore, the end part 42 and the protrusion part 30 of the heater 40 may be joined by brazing, for example.

DESCRIPTION OF SYMBOLS 1 ... Impregnation type | mold cathode structure, 10 ... Cathode base, 12 ... Electron emission surface of a cathode base, 14 ... Back surface of a cathode base, 20 ... Support body, 22 ... Storage space, 24 ... Support outer cylinder, 25 ... Support outer cylinder Flange portion, 26 ... support inner cylinder, 28 ... occlusion plate, 30 ... protruding portion, 32 ... platinum ribbon, 40 ... heater, 42 ... heat generating portion of heater, 44,46 ... end portion of heater, 48 ... alumina tube, 50 DESCRIPTION OF SYMBOLS ... Embedded material, 60 ... 1st reflecting plate, 61 ... Notch of 1st reflecting plate, 62 ... 2nd reflecting plate, 64 ... Spacer, 66 ... Reflecting cylinder, 68 ... Flange member

Claims (7)

A cathode substrate impregnated with an electron emitting material;
A support outer cylinder, and a support inner cylinder disposed 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, A support body on which a cathode base is attached to support the cathode base, and a protruding portion protruding from one end surface of the support inner cylinder;
A heater formed in a linear shape, at least a part of which is stored in the storage space of the support, and one end of which is joined to the protruding portion outside the storage space of the support;
An embedding material filled in a storage space of the support;
An impregnated cathode structure characterized by comprising:   2. The impregnated-type cathode assembly according to claim 1, wherein the protruding portion and one end portion of the heater are joined by welding.   2. The impregnated-type cathode assembly according to claim 1, wherein the projecting portion and one end portion of the heater are joined by platinum.   4. The impregnated-type cathode assembly according to claim 3, wherein the protrusion and one end of the heater are joined by dissolving a platinum ribbon.   The impregnated-type cathode assembly according to any one of claims 1 to 4, wherein the support inner cylinder is made of a metal material, and the embedding material is made of an insulating material.   6. The impregnated-type cathode assembly according to claim 1, wherein the protrusion is formed in a rectangular parallelepiped shape.   The impregnated-type cathode assembly according to claim 6, wherein an outer periphery of one end portion of the heater 40 is joined to one side surface of the rectangular parallelepiped protruding portion.

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