Magnetron

Abstract

To provide a magnetron with a novel structure in which the cathode is, in principle, not subjected to back bombardment by electrons.SOLUTION: A magnetron 100 includes a cylindrical anode body 10 in which a plurality of resonant cavities 60 are formed, a cathode body 20 arranged on the central axis of the anode body, and a pair of magnetic poles 30a, 30b that apply a magnetic field parallel to the central axis to an action space 50 surrounded by the inner surface at the portion where the resonant cavities of the anode body are formed. The cathode body has an electron emitter 22 that emits electrons in a direction parallel to the central axis, and the electron emitter is arranged at a distance from the action space in the direction of the central axis.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a magnetron that oscillates microwaves. [Background technology]

[0002] A typical magnetron is composed of a cylindrical anode and a cathode arranged on the central axis of the anode. A number of anode vanes are formed radially from the inner peripheral surface of the anode toward the central axis, and a resonant cavity is formed between adjacent anode vanes. The cathode is composed of, for example, a coil-shaped filament, and an interaction space in which electrons move due to an electromagnetic field is formed between the anode vanes and the cathode. A magnetic field is applied to the interaction space in the direction of the central axis.

[0003] In a magnetron with such a configuration, electrons are emitted from the cathode toward the anode vanes by applying a current to the cathode filament and a voltage between the anode and the cathode. The electrons emitted from the cathode orbit the cathode due to the effect of the magnetic field applied to the interaction space, and energy due to the electron motion is imparted to the resonant cavity, generating microwaves in the resonant cavity.

[0004] However, among the electrons emitted from the cathode into the interaction space, those with slower movement speeds return to the cathode due to the effect of the magnetic field and back bombard the cathode. If the cathode is subjected to back bombardment by electrons for a long period of time, the cathode will be corroded, which is a factor in shortening the life of the magnetron.

[0005] As a method for preventing corrosion of the cathode, Patent Document 1 discloses an indirectly heated cathode having a structure in which unevenness is provided on the surface of a cylindrical metal substrate, and the recesses are filled with a thermoelectron emitting material. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2000-299069 A Summary of the Invention [Problem to be solved by the invention]

[0007] The indirectly heated cathode having the structure disclosed in Patent Document 1 reduces the exposed area of ​​the thermoelectron emitting material, thereby reducing the rate at which it is subjected to back bombardment by electrons. However, the thermoelectron emitting material filled in the recesses is still subjected to back bombardment by electrons, and this does not provide a fundamental solution to prevent corrosion of the cathode.

[0008] The present invention provides a magnetron of a novel structure in which the cathode is, in principle, not subjected to back bombardment by electrons. [Means for solving the problem]

[0009] The magnetron of the present invention comprises a cylindrical anode body in which a plurality of resonant cavities are formed, a cathode body arranged on the central axis of the anode body, and a pair of magnetic poles that impart a magnetic field parallel to the central axis to an action space surrounded by the inner surface at the portion of the anode body where the resonant cavities are formed, the cathode body having an electron emission source that emits electrons toward the action space in the direction of the central axis, and the electron emission source is arranged at a distance from the action space in the direction of the central axis. Effect of the Invention

[0010] According to the present invention, it is possible to provide a magnetron of a novel structure in which the cathode is not, in principle, subjected to back bombardment by electrons. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a cross-sectional view showing a schematic structure of a magnetron in the present embodiment. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 13 is a diagram showing an electric field applied to an interaction space. [Figure 4] 3 is a cross-sectional view showing a schematic diagram of a trajectory of an electron emitted from an electron emission source. FIG. [Diagram 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 11 is a cross-sectional view showing a schematic configuration of the cathode body. [Figure 7] FIG. 11 is a cross-sectional view showing a schematic configuration of an anode body. [Figure 8] FIG. 1 is a cross-sectional view showing a schematic structure of a conventional magnetron. [Figure 9] FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. [Figure 10] FIG. 13 is a diagram showing an electric field applied to an interaction space. [Figure 11] FIG. 2 is a cross-sectional view showing a schematic diagram of a trajectory of an electron emitted from a cathode. [Figure 12] 12 is a cross-sectional view taken along line XII-XII in FIG. 11. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Fig. 8 is a cross-sectional view showing a typical structure of a conventional magnetron, and Fig. 9 is a cross-sectional view taken along line IX-IX in Fig. 8.

[0013] 8 and 9, a conventional magnetron is composed of a cylindrical anode 110 and a cathode 120 arranged on a central axis J of the anode 110. A plurality of anode vanes 111 are formed radially from the inner peripheral surface of the anode 110 toward the central axis J, and a resonant cavity 160 is formed in the space between adjacent anode vanes 111.

[0014] The cathode 120 is made of, for example, a coil-shaped filament, and an interaction space 150 in which electrons move due to an electromagnetic field is formed between the anode vane 111 and the cathode 120. A pair of pole pieces (magnetic poles) 130a, 130b that apply a magnetic field parallel to the central axis J direction to the interaction space 150 are disposed on both sides of the anode vane 111 in the direction of the central axis J.

[0015] In such a configuration, when a current is passed through the filament of the cathode 120 and a voltage is applied between the anode 110 and the cathode 120, an electric field E perpendicular to the central axis J is applied in the interaction space 150 from the cathode 120 toward the anode vane 111, as shown in Figure 10, and electrons are emitted from the cathode 120 toward the anode vane 111.

[0016] Electrons emitted from the cathode 120 rotate around the cathode 120 in the interaction space 150, drawing a spiral due to the effect of the magnetic field applied in a direction parallel to the central axis J, and reach the anode vanes 111. At this time, energy due to the electron motion is provided to the resonant cavity 160, generating microwaves in the resonant cavity 160. The microwaves generated in the resonant cavity 160 are output to the outside via the antenna 140.

[0017] FIG. 11 is a cross-sectional view that shows a schematic diagram of the trajectory of electrons emitted from the cathode 120, and FIG. 12 is a cross-sectional view taken along line XII-XII in FIG.

[0018] As shown in Fig. 10, an electric field E perpendicular to the central axis J is applied to the interaction space 150, so that the electrons emitted from the cathode 120 into the interaction space 150 rotate around the cathode 120 in a spiral on a plane perpendicular to the central axis J, as shown by the trajectory of the arrow A, and reach the anode vane 111. However, among the electrons emitted from the cathode 120 into the interaction space, some electrons with a slower moving speed do not reach the anode vane 111, but return to the cathode 120 by the action of the magnetic field, as shown by the trajectory of the arrow B, and back bombard the cathode 129. In this way, when the cathode 120 is subjected to back bombardment by electrons for a long period of time, the cathode 120 is corroded, which is a factor that shortens the life of the magnetron.

[0019] The present invention provides a magnetron having a novel structure in which the cathode is, in principle, not subjected to back bombardment by electrons. Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0020] FIG. 1 is a cross-sectional view showing a schematic structure of a magnetron in this embodiment, and FIG. 2 is a cross-sectional view taken along line II-II in FIG.

[0021] 1 and 2, a magnetron 100 in this embodiment is composed of a cylindrical anode body 10 and a cathode body 20 arranged on a central axis J of the anode body 10. The anode body 10 includes an anode cylinder 11 and a plurality of anode vanes 12 extending radially from the inner peripheral surface of the anode cylinder 11 toward the central axis J, and a plurality of resonant cavities 60 are formed by the anode cylinder 11 and the plurality of anode vanes 12.

[0022] An action space 50 in which electrons move due to an electromagnetic field is formed on the inner circumferential surface of the anode body 10 at the portion where the resonant cavity 60 is formed, i.e., in a space surrounded by the inner circumferential surface of an envelope circle connecting the tips of the multiple anode vanes 12. A pair of pole pieces (magnetic poles) 30a, 30b are disposed on both sides of the anode vane 12 in the direction of the central axis J to impart a magnetic field parallel to the direction of the central axis J to the action space 50.

[0023] The cathode body 20 is an indirectly heated cathode made up of a cylindrical sleeve 21 with a heater 23 built in therein, and an electron emission source (emitter) 22 provided on an end surface of the sleeve 21. The electron emission source 22 has a surface perpendicular to the central axis J, and is disposed apart from the interaction space 50 in the direction of the central axis J. Electrons are emitted from the electron emission source 22 by heating the heater 23 to heat the end surface of the sleeve 21 that is in contact with the electron emission source 22. The electron emission source 22 is made of a material such as tungsten or tantalum.

[0024] In such a configuration, when a voltage is applied between the anode body 10 and the cathode body 20, an electric field E is applied in the interaction space 50 from the cathode body 20 toward the anode vane 12, as shown in Figure 3, the electric field E having a component perpendicular to the central axis J and a component parallel to the central axis J and directed away from the electron emission source 22.

[0025] FIG. 4 is a cross-sectional view that diagrammatically shows the trajectory of electrons emitted from the electron emission source 22, and FIG. 5 is a cross-sectional view taken along line VV in FIG.

[0026] As shown in FIG. 3, in the action space 50, an electric field E having a component perpendicular to the central axis J and a component parallel to the central axis J and moving away from the electron emission source 22 is applied from the cathode body 20 toward the anode vane 12. As a result, the electrons emitted from the electron emission source 22 into the action space 50 to which a magnetic field parallel to the central axis J is applied are subjected to not only the electric field E having a component perpendicular to the central axis J, but also the force from the electric field E having a component parallel to the central axis J and moving away from the electron emission source 22. Therefore, the electrons emitted from the electron emission source 22 into the action space 50 reach the anode vane 12 while rotating around the central axis J in a direction moving away from the electron emission source 22 and drawing a spiral, as shown by the trajectory of the arrow A. At this time, energy due to the electron motion is applied to the resonant cavity 60, and microwaves are generated in the resonant cavity 60. The microwaves generated in the resonant cavity 60 are output to the outside via the antenna 40.

[0027] On the other hand, among the electrons emitted from the electron emission source 22 into the interaction space 50, those moving at a slower speed do not return to the electron emission source 22, but instead rotate around the central axis J in a direction away from the electron emission source 22, increasing the number of times, as shown by the trajectory of the arrow B, and reach the anode vane 12 while drawing a spiral. In other words, the electron emission source 22 is not subjected to reverse impact by the electrons.

[0028] In this embodiment, the electron emission source 22 is disposed in the working space 50 at a distance from the working space 50 in the direction of the central axis J, so that an electric field E having a component perpendicular to the central axis J and a component parallel to the central axis J and moving away from the electron emission source 22 is applied from the cathode body 20 toward the anode vane 12 in the working space 50. Therefore, the force of the electric field that returns the electrons emitted from the electron emission source 22 to the working space 50 is not applied, so that the electron emission source 22 is not subjected to a back impact of the electrons in principle. As a result, the life of the magnetron can be dramatically extended. In addition, the electrons emitted from the electron emission source 22 reach the anode vane 12 without returning to the electron emission source 22, so that the electron collection efficiency is improved and it is possible to simultaneously achieve a high microwave output.

[0029] Although the present invention has been described above with reference to preferred embodiments, these descriptions are not limiting and various modifications are possible. For example, in the above embodiment, an indirectly heated cathode having an electron emission source 22 provided on the end face of a cylindrical sleeve 21 is exemplified as the cathode body 20, but as shown in FIG. 6, a pair of gate electrodes 70a, 70b may be disposed on either side of the electron emission source 22 to control the emission of electrons from the electron emission source 22.

[0030] Moreover, the cathode body 20 is not limited to an indirectly heated cathode, but may be a directly heated cathode or a field emission cathode. In the former case, the electron emission source 22 is composed of a filament that is heated by passing current and emits electrons, while in the latter case, the electron emission source 22 is composed of an emitter electrode that emits electrons by applying a strong electric field.

[0031] In the above embodiment, the anode body 10 has been exemplified as having a structure including a plurality of anode vanes 12 extending radially from the inner circumferential surface of the anode cylinder 11 toward the central axis J, but the present invention is not limited thereto and may be any anode body in which a plurality of resonant cavities are formed. For example, as shown in Fig. 7, the anode body 10 may have a structure in which a plurality of cavities 60 are formed in the circumferential direction in a cylindrical anode body 10. In this case, the plurality of cavities 60 form a resonant cavity, and each of the cavities 60 communicates with an action space 50 surrounded by the inner circumferential surface of the anode body 10 via a slit 80. [Explanation of symbols]

[0032] 10 Anode body 11 Anode cylinder 12 Anode vane 20 Cathode body 21 Sleeve 22 Electron emission source 23 Heater 30a, 30b pole pieces (magnetic poles) 40 Antenna 50 Working space 60 resonant cavity 70a, 70b Gate electrode 80 Slit 100 Magnetron

Claims

1. A cylindrical anode body having a plurality of resonant cavities formed therein; A cathode body disposed on the central axis of the anode body; a pair of magnetic poles for applying a magnetic field parallel to the central axis to an action space surrounded by an inner circumferential surface at a portion where a resonant cavity of the anode body is formed; A magnetron comprising: the cathode body has an electron emission source that emits electrons in a direction parallel to the central axis, The electron emission source is disposed at a distance from the interaction space in the direction of the central axis.

2. 2. The magnetron according to claim 1, wherein the cathode body is composed of a cylindrical sleeve having a heater built therein, and the electron emission source provided on an end surface of the sleeve.

3. The anode body includes an anode cylinder and a plurality of anode vanes extending radially from an inner peripheral surface of the anode cylinder toward the central axis, the anode cylinder and the plurality of anode vanes form the plurality of resonant cavities; The magnetron according to claim 1 , wherein the working space is defined by an inner peripheral surface of an envelope circle connecting the tips of the plurality of anode vanes.

4. 2. The magnetron according to claim 1, further comprising a pair of gate electrodes arranged on either side of the electron emission source for controlling emission of electrons from the electron emission source.

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