JP2020064804A - Magnetron - Google Patents

Abstract

To increase life by increasing an amount of adsorption of a gas, and to eliminate high cost and poor operation due to deformation of a getter material.SOLUTION: A magnetron includes: a cathode 2 coated or impregnated with an electron radiation material; a cylindrical cathode sleeve 3 supporting the cathode 2; and an end hat provided at an end of the cathode sleeve 3. A stopper section 8 is formed at an end of the cathode sleeve 3. As the end hat, first end hat members 5a, 5b made of hafnium having a getter action and second end hat members 6a, 6b made of molybdenum are provided. The first end hat members 5a, 5b are caulked and fastened to the stopper section 8. The second end hat members 6a, 6b are fixed to the cathode sleeve 3 by welding.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnetron, and more particularly to a structure of a magnetron cathode having a long life while maintaining stable characteristics.

  The magnetron comprises a cylindrical anode, a plurality of vanes arranged on the inner surface of the anode, and a cylindrical cathode provided inside the vane, and a magnetic field applied in the axial direction of the anode and the cathode This is a device for obtaining high-frequency output power by causing electrons radiated from the cathode to rotate and orbit by a high voltage applied between the cathodes, to induce and oscillate a high-frequency electric field in the resonator formed by the vanes.

The electrons emitted from the cathode are also subjected to a force in the axial direction of the cathode due to the electric charge, tend not to reach the vanes, and tend to leak in the axial direction. To prevent the leakage of electrons in the axial direction, Place end hats on both ends of the cathode.
Further, in order to extract electrons from the cathode, the cathode is coated or impregnated with barium oxide, which is an electron emissive substance, and the cathode is heated to emit thermoelectrons. However, since the electron emissive material of the cathode is decomposed and liberated during operation and becomes a gas source that deteriorates the degree of vacuum in the magnetron tube, it is normally necessary to prevent the deterioration of the degree of vacuum due to operation in the magnetron tube. A substance having a getter action is placed in the sphere.

Conventionally, there is known a structure in which a getter material having a getter action is attached to end hats at both ends of a cathode by a method such as vapor deposition, pressure bonding / sintering, and welding. In addition, as a known technique, there are techniques disclosed in Patent Documents 1 to 4 below.
That is, since the end hat of this cathode is in the vicinity of the electron emissive material which is the gas source, it is suitable as a place for installing the getter material. Further, since the cathode is heated to emit electrons, the temperatures of the end hats and getter materials installed at both ends of the cathode are also appropriately increased, which activates the getter material and removes the gas attached to the getter material. The rate of diffusion to the inside is increased, and its action enhances the gas adsorption capacity. In this way, the getter material works effectively in maintaining the degree of vacuum.

Japanese Patent Laid-Open No. 11-250816, Japanese Patent Laid-Open No. 05-251005 Japanese Patent Publication No. 07-60639 JP-A-63-226851

  By the way, as described above, the getter material is attached to the end hat by vapor deposition, pressure bonding and sintering, or attached to the end hat by welding, but when the getter material is attached by vapor deposition, the amount of the getter material is large. It is difficult to do so, and with a small amount of getter material, only a small amount of gas can be adsorbed, and the effect of maintaining the degree of vacuum for a long time cannot be expected.

Further, when the getter material is attached to the end hat in the pressure-bonding / sintering process, the pressure-bonding / sintering process requires time, resulting in high cost.
Furthermore, when a plate-shaped getter material is attached to the end hat by welding, it is difficult to prevent the getter material from being deformed due to high temperature during operation (also shown in Patent Document 4). There is a problem that defects and deterioration of characteristics are likely to occur.

  The present invention has been made in view of the above problems, and an object thereof is to increase the amount of adsorbed gas to prolong the life, and to increase the cost, and eliminate malfunctions due to deformation of the getter material. To provide a magnetron that can.

In order to achieve the above object, the magnetron according to the invention of claim 1 is arranged at the center of an anode, and has a cathode coated or impregnated with an electron emissive material, a cylindrical cathode sleeve for supporting the cathode, and In a magnetron having an end hat provided at an end portion of the cathode sleeve, a stopper portion is formed at the end portion of the cathode sleeve, the end hat is made of a different material, and one of them has a getter action. A first end-hat member and a second end-hat member made of a certain material are provided, and the first end-hat member is attached to the stopper portion of the cathode sleeve by contacting the stopper portion of the cathode sleeve. The second end hat member is attached in contact therewith.
According to a second aspect of the present invention, in the end hat, the first end hat member arranged near the electron emitting surface of the cathode is made of a material having a getter action. The closely contacted second end hat member is made of the same material as the cathode sleeve, and the second end hat member and the cathode sleeve are welded.
According to a third aspect of the present invention, in the end hat, the first end hat member at a position close to the electron emitting surface of the cathode is formed of a refractory metal, and the surface thereof is carbonized to form a second end hat member. It is characterized by being made of a material having a getter action.

According to the invention of claim 1 or 2, the gas emitted from the electron emission surface by forming one of the first end hat member and the second end hat member with a material having a getter action (getter material). Can be effectively adsorbed, the degree of vacuum can be maintained for a long time, and a long-life magnetron can be obtained.
Further, unlike the conventional case, since the step of pressure-bonding / sintering for attaching the getter material is not adopted, the cost does not increase, and the first or second end hat member made of the getter material is welded to the cathode sleeve. Therefore, it is possible to eliminate the deformation of the member made of the getter material due to the high temperature during operation and to eliminate the trouble of magnetron operation.

  According to the invention of claim 3, not only the gas emitted from the electron emission surface is effectively adsorbed by the second end hat member having a getter action, but also the first end hat member close to the electron emission surface is carbonized. Since it is formed of the refractory metal described above, it is possible to reduce the emission of secondary electrons from the end hat and eliminate the decrease in output power. That is, in the operation of the magnetron, a part of the electrons in the tube receives the energy of microwaves to go backward and collide with the cathode and the end hat. At that time, secondary electrons are generated by the electrons colliding with the end hat, which causes the increase in the dark current of the magnetron. Since the refractory metal having a carbonized surface has a small secondary electron emission coefficient, the first end hat close to the electron emission surface is formed of a carbonized refractory metal, so that the The emission of secondary electrons can be reduced, and a magnetron with less dark current can be obtained.

FIG. 1 is a sectional view showing the structure of a magnetron according to a first embodiment of the present invention. It is sectional drawing which shows the attachment state of the end hat of 1st Example, and another structural example. It is sectional drawing which shows the structure of the attachment part of the end hat in the magnetron of 2nd Example.

  FIG. 1 shows the configuration of the magnetron of the embodiment, and FIG. 2 (A) shows the mounting state of the end hat. In FIG. 1, reference numeral 1 is a cylindrical anode, 2 is the center of the anode. A cylindrical cathode 3 provided at the end of the cathode sleeve, 3 a cylindrical cathode sleeve supporting the cathode, 4 heaters 5a and 5b provided at both ends of the cathode sleeve 3, and a first end having a disk-shaped portion. The hat members 6a, 6b are second end hat members attached to the outside of the first end hat members 5a, 5b at both ends of the cathode sleeve 3 and having a disk-shaped portion, and the end hat of the embodiment is It is composed of first and second end hat members 5a, 6a and 5b, 6b.

  The cathode 2 is made of porous tungsten and is an impregnated cathode in which the hole portion of the cylindrical wall is impregnated with an electron emissive substance such as barium. By heating the cathode 2 in the evening 4, the thermoelectrons are taken out. be able to.

  The cathode sleep 3 is made of molybdenum, and has stopper portions (locking portions) 8 [see FIG. 2 (A)] having a step with a small outer diameter of the cylinder formed on both axial ends thereof. The first end hat members 5a, 5b of the first embodiment are made of hafnium having a getter action, and since this material is difficult to weld with other materials, the stopper portion 8 of the cathode sleep 3 made of molybdenum is used. It is fastened by caulking.

  The second end hat members 6a and 6b are made of molybdenum and are fixed to the cathode sleeve 3 by welding. The second end hat members 6a, 6b are in close contact with the first end hat members 5a, 5b, and are securely fixed to the cathode sleeve 3 by welding, so that the first end hat members 5a, 5b are also fixed. It can be firmly fixed, and even if the caulking of the first end hat members 5a and 5b is loosened, the position thereof does not shift.

The end hat composed of the first and second end hat members 5a, 6a, 5b, 6b increases the electric field strength generated by a high voltage applied between the cathode 2 and the anode 1 at the end hat portion to increase the cathode 2 It acts so as to suppress the electrons escaping in the axial direction of the cathode side.
Both the first end hat members 5a and 5b and the second end hat members 6a and 6b have a function of suppressing such escape of electrons, and the outer diameters of both end hat members are set to be substantially the same. ing. Further, by providing the two end hat members 5a, 6a, 5b, 6b at both ends, the effect of suppressing electrons becomes greater than in the case where only one end hat is provided. Of course, in the case of an end hat having a size in which the first end hat members 5a and 5b and the second end hat members 6a and 6b are united into one, the action of suppressing electrons is the same as that of the two end hat members. Is equivalent.

However, if one large end hat is made of a material having a getter action, it is difficult to weld it to the cathode sleeve 3 made of a different material, that is, molybdenum, and the large end hat is stopped only by caulking. Therefore, there is concern about the mounting strength.
For example, in a structure in which a getter material is attached to a mountain portion of an end hat as in the related art (for example, Patent Document 3), it is difficult to fix the getter material to the end hat and suppress deformation at high temperature due to operation. .

  Therefore, in the embodiment, of the two end hat members, the first end hat members 5a, 5b themselves are made of a metal having a getter action, and the first end hat members 5a, 5b are welded together. By using the shape in which the second end hat members 6a and 6b are pressed, it is possible to minimize positional deviation and deformation, and eliminate malfunctions (deterioration of characteristics).

  In the magnetron, since the electric field strength between the end hat and the anode is large, when barium or the like (gas) which is an electron emitting substance is scattered or diffused from the cathode 2 and adheres to the end hat, secondary electrons are emitted from the part. The electrons and the current easily become reactive current that does not contribute to high-frequency oscillation. The amount of the electron emissive material attached to the end hat increases with the operation, and accordingly, the dark current increases, which causes a decrease in transmission power and shortens the life of the magnetron.

  However, if a material having a getter action is used for the first end hat members 5a and 5b as in the embodiment, the gettering of the electron emissive substance adhered to the first end hat members 5a and 5b due to scattering and diffusion is prevented. By the action, the magnetron is taken into the inside of the member, the emission of the secondary electrons from the end hat is suppressed, and the increase of the dark current is suppressed, so that a long-life magnetron can be realized.

  Hafnium was used as the material having a getter action as the first end hat members 5a and 5b in the first embodiment, but zirconium or titanium may be used, and even if they are used, the action and effect are similar to those of hafnium. Becomes

  FIG. 2 (B) shows another structure of the stopper portion. Instead of the step portion as shown in FIG. 2 (A), the stopper portion 9 having a convex portion may be formed. The first end hat members 5a and 5b may be caulked to the convex portion of the stopper portion 9 and the second end hat members 6a and 6b may be welded to the cathode sleeve 3. Further, the convex stopper portion 9 may be formed separately from the cathode sleeve 3, and may be attached to the cathode sleeve 3 by brazing or welding.

FIG. 3 shows the configuration of the second embodiment of the present invention. In this second embodiment, the end hat member is carbonized. The first end hat member 15 in FIG. 3 is made of molybdenum which is a high melting point metal, and the second end hat member 16 is made of hafnium having a getter action.
The first end hat member 15 has the portion 50 shown by the dotted line carbonized, and the rest of the configuration is the same as in the case of FIG. Further, the first end hat member 15 is arranged on the stopper portion 8 formed on the cathode sleeve 3, and the second end hat member 16 is crimped to the cathode sleeve 3 by the caulking portion 17.

  As described above, during the operation of the magnetron, some of the electrons emitted from the cathode 2 go back and collide with the cathode 2 and the end hat, and when secondary electrons are generated from the electrons colliding with the end hat, The secondary electrons become electrons and current that do not contribute to the output power as reactive current. In the second embodiment, the property of molybdenum that the secondary electron emission coefficient is reduced by carbonization of the surface is utilized, and the first end hat member 15 is carbonized molybdenum, so that the secondary electrons from that part are generated. It is possible to realize a magnetron that suppresses emission, suppresses reactive current, and does not reduce output power.

  Further, since hafnium, which is a metal having a gettering action, is used as the second end hat member 16, the second end hat member 16 acts so as to maintain the degree of vacuum in the magnetron tube and has a long life. It becomes a magnetron.

1 ... Anode, 2 ... Cathode,
3 ... Cathode sleeve, 4 ...
5a, 5b, 15 ... First end hat member,
6a, 6b, 16 ... Second end hat member,
8, 9 ... Stopper part,
50 ... Carbonized portion.

Claims (3)

In a magnetron having a cathode arranged at the center of an anode and coated or impregnated with an electron emitting substance, a cylindrical cathode sleeve supporting the cathode, and an end hat provided at an end portion of the cathode sleeve,
Forming a stopper at the end of the cathode sleeve,
As the end hat, a first end hat member and a second end hat member, each of which is made of a different material and one of which is a material having a getter action, are provided.
A magnetron comprising: a first end hat member attached to the stopper portion of the cathode sleeve; and a second end hat member attached to the first end hat member.   In the above-mentioned end hat, the first end hat member arranged near the electron emitting surface of the cathode is made of a material having a getter action, and the second end which is closely attached to the first end hat member. The magnetron according to claim 1, wherein the hat member is made of the same material as that of the cathode sleeve, and the second end hat member and the cathode sleeve are welded to each other. In the end hat, the first end hat member at a position near the electron emission surface of the cathode is formed of a refractory metal, and the surface thereof is carbonized, and the second end hat member is made of a material having a getter action. The magnetron according to claim 1, wherein the magnetron is formed.

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