JP2017004778A - Electron gun for microwave tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electron gun for microwave tube capable of reducing occurrence of gun oscillation in electron gun's own structure.SOLUTION: An electron gun 12 for a microwave tube comprises a cathode 23, an anode 26, a Wehnelt electrode 25 and a housing 27. The cathode 23 emits an electron beam. The anode 26 opposes to the cathode 23. The Wehnelt electrode 25 is disposed around the cathode 23, includes an inclined slope 34 of which the diameter is reduced in a direction away from the anode 26, at a back side opposite to the anode 26 and converges the electron beam that is emitted from the cathode 23. The housing 27 includes a wall part 36 that includes the cathode 23 and the Wehnelt electrode 25 and in the wall part 36, an inclined inner wall surface 37 is provided which is inclined in the same direction as the inclined plane 34 of the Wehnelt electrode 25.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to an electron gun for a microwave tube.

  There is a klystron as a microwave tube. In this klystron, an electron beam extracted from an electron gun passes through the anode and is introduced into the cavity, and is then captured by the collector. A high frequency input signal input from an input cavity close to the electron gun is amplified by an electron beam to become a high frequency output, and is output from an output window connected to the output cavity.

  The high-frequency output needs to be a pulse waveform that corresponds to the input signal waveform, but depending on the structure of the adopted electron gun, oscillation at a specific frequency occurs due to a phenomenon called “gun oscillation”. A part of the output waveform appears as a part of the output waveform is consumed. In this case, problems such as a decrease in energy efficiency in the klystron, a malfunction of amplification due to beam modulation, and a local load applied to the tube structure occur.

  For this reason, in order to maintain the efficiency and stable operation of the klystron, it is necessary to suppress oscillation at frequencies other than the intended purpose.

  There is a proposal to suppress the occurrence of gun oscillation by arranging a radio wave absorber in the housing of the electron gun.

  However, since it is necessary to dispose a radio wave absorber as a separate part in the housing of the electron gun, it is desired that the generation of gun oscillation can be reduced by the structure of the electron gun itself.

JP-A-9-161687

  The problem to be solved by the present invention is to provide an electron gun of a microwave tube that can reduce the occurrence of gun oscillation with the structure of the electron gun itself.

  The electron gun of the microwave tube of this embodiment includes a cathode, an anode, a Wehnelt electrode, and a housing. The cathode emits an electron beam. The anode faces the cathode. The Wehnelt electrode is disposed around the cathode, and is provided with an inclined surface whose diameter decreases toward the direction away from the anode on the back side opposite to the anode, and focuses the electron beam emitted from the cathode. The housing has a wall portion that encloses the cathode and the Wehnelt electrode, and an inclined inner wall surface that is inclined in the same direction as the inclined surface of the Wehnelt electrode is provided on the wall portion.

It is sectional drawing of the electron gun of the microwave tube which shows one Embodiment. It is sectional drawing of a microwave tube same as the above. It is a wave form diagram of the input pulse waveform of a microwave tube same as the above. It is a wave form diagram of the output pulse waveform influenced by the gun oscillation of a microwave tube same as the above.

  Hereinafter, an embodiment will be described with reference to FIGS. 1 to 4.

  FIG. 2 shows a cross-sectional view of the klystron 10 as a microwave tube.

  The klystron 10 captures the electron gun 12 that is the starting point of the electron beam 11, the cavity 13 that amplifies the high frequency by the energy of the electron beam 11 generated by the electron gun 12, and the electron beam 11 that passes through the cavity 13 And a collector 14 for cooling, a high frequency input port 15 for inputting a high frequency to the cavity 13, and a high frequency output window 16 for extracting the high frequency amplified by the cavity 13.

  The klystron 10 includes an exhaust pipe 17 for performing a baking process while evacuating the inside of the klystron 10, and a vacuum pump 18 for discharging a gas released from the tube when the klystron 10 is operated. The exhaust pipe 17 is sealed after the baking is finished. The vacuum pump 18 is a sealed type such as an ion pump or a getter type pump.

  Around the electron gun 12 and the cavity 13, a counter coil 19 and a focusing coil that form a magnetic field parallel to the axial direction of the klystron 10 so that the electron beam 11 is not incident on the inner wall of the cavity 13 and lost. 20 are arranged respectively. Further, the vicinity of the entrance of the cavity portion 13 is formed in a tapered shape that expands toward the electron gun 12 side so that the electron beam 11 is not incident on the inner wall of the cavity portion 13 and lost.

  FIG. 1 shows a cross-sectional view of the electron gun 12 of the klystron 10.

  The electron gun 12 includes a cathode 23 that emits an electron beam 11, a heater 24 that heats the cathode 23 to emit thermal electrons, a Wehnelt electrode 25 that focuses and shapes the electron beam 11 emitted from the cathode 23, a cathode An anode 26 for extracting electrons from 23, and a housing 27 for housing them are provided.

  The cathode 23 is supported by a cathode support flange 28.

  The heater 24 includes a pair of heater terminals 29a and 29b for supplying power. One heater terminal 29a is connected to the cathode support flange 28, and the other heater terminal 29b is connected to the Wehnelt support cylinder 30 and the electron gun support flange 31. The cathode support flange 28 and the Wehnelt support cylinder 30 are connected via an insulating cylinder 32.

  The Wehnelt electrode 25 is disposed around the cathode 23 by a Wehnelt support cylinder 30. The Wehnelt support cylinder 30 is supported by the electron gun support flange 31. A tip portion 33 that is curved in the radial direction is provided at the tip of the Wehnelt electrode 25 that faces the anode 26. On the outer surface of the Wehnelt electrode 25 and on the back side opposite to the anode 26, there is provided an inclined surface 34 whose diameter decreases from the tip 33 in a direction away from the anode 26. The inclined surface 34 may be a flat surface or a curved surface.

  The anode 26 is provided at the entrance of the cavity 13 and faces the cathode 23.

  The housing 27 includes a support portion 35 that is a flange that supports the anode 26, a cylindrical wall portion 36 that encloses the cathode 23, the Wehnelt electrode 25, and the like. An inclined inner wall surface 37 that is inclined in the same direction as the inclined surface 34 of the Wehnelt electrode 25 is provided on the inner peripheral surface of the wall portion 36. That is, the inclined inner wall surface 37 is reduced in diameter from the support portion 35 in a direction away from the anode 26. Note that the distance between the inclined surface 34 of the Wehnelt electrode 25 and the inclined inner wall surface 37 of the housing 27 is preferably constant.

  Between the wall portion 36 of the housing 27 and the electron gun support flange 31, a high voltage is applied between the anode 26 via the housing 27 and the cathode 23 and Wehnelt electrode 25 via the electron gun support flange 31. On the other hand, an insulating cylinder 38 for maintaining insulation is provided.

  In the klystron 10 shown in FIG. 2, the electron beam 11 extracted from the electron gun 12 passes through the anode 26 and is introduced into the cavity 13 and then captured by the collector 14. The high-frequency input signal input from the high-frequency input port 15 to the input cavity close to the electron gun 12 in the cavity 13 is amplified by the electron beam 11 to become a high-frequency output, and is connected to the output cavity of the cavity 13 Is output from the high frequency output window 16.

  As shown in FIG. 3, a high-frequency input signal having a flat top pulse waveform is input from the high-frequency input port 15, but oscillation at a specific frequency occurs in the electron gun 12 due to a phenomenon called “gun oscillation”. In this case, as shown in FIG. 4, a part of the energy of the input waveform is consumed, and a part of the output waveform appears missing. In this case, problems such as a decrease in energy efficiency in the klystron 10, a malfunction of amplification due to beam modulation, and a local load applied to the tube structure occur.

  As shown in FIG. 1, the gun oscillation is supposed to be caused by a high frequency of an unnecessary frequency staying in a region 40 inside the wall portion 36 of the housing 27. Therefore, in order to suppress cancer oscillation, it is effective to make the shape of the internal structure in this region 40 a structure in which high frequency does not stay easily.

  Therefore, on the outer surface of the Wehnelt electrode 25 and on the back side opposite to the anode 26, an inclined surface 34 whose diameter is reduced from the tip portion 33 in the direction away from the anode 26 is provided, and the inner surface of the wall portion 36 of the housing 27 An inclined inner wall surface 37 that is inclined in the same direction as the inclined surface 34 of the Wehnelt electrode 25 is provided on the peripheral surface.

  With this configuration, the gap between the inclined surface 34 of the Wehnelt electrode 25 and the inclined inner wall surface 37 of the housing 27 can be reduced, and discontinuous portions of the high-frequency transmission impedance can be reduced. High frequency can easily flow, and high frequency can be prevented from staying in the region 40.

  Further, by making the distance between the inclined surface 34 of the Wehnelt electrode 25 and the inclined inner wall surface 37 of the housing 27 constant, it is possible to further suppress the high frequency from staying in the region 40.

  In this way, the klystron 10 can suppress the stagnation of unnecessary high frequencies in the region 40 where gun oscillation occurs in the klystron 10, thereby suppressing the disturbance of the output waveform and maintaining the waveform corresponding to the input waveform. Ten electron guns 12 can be provided.

  Although a klystron is shown as a microwave tube, it can also be applied to other microwave tubes such as a traveling wave tube and a gyrotron.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example 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 scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

10 Klystron as a microwave tube
11 Electron beam
12 electron gun
23 Cathode
25 Wehnelt electrode
26 Anode
27 Housing
34 Inclined surface
36 Wall
37 Inclined inner wall

Claims (2)

A cathode that emits an electron beam;
An anode facing the cathode;
An inclined surface disposed around the cathode and having a diameter reduced toward the direction away from the anode is provided on the back side opposite to the anode, and focuses the electron beam emitted from the cathode. A Wehnelt electrode;
And a housing having a wall portion that encloses the cathode and the Wehnelt electrode, and an inclined inner wall surface that is inclined in the same direction as the inclined surface of the Wehnelt electrode. Microwave tube electron gun. The electron gun for a microwave tube according to claim 1, wherein a distance between the inclined surface of the Wehnelt electrode and the inclined inner wall surface of the housing is constant.

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