JPH052994A - Electron gun for microwave tube with straight advancing beam - Google Patents

Abstract

PURPOSE:To hinder an electron beam generated at the time of cut off from being fed into a high frequency circuit and prevent generation of noize by furnishing the cathode of an electron gun with a checking member to check emission of electron beam at the center of the cathode. CONSTITUTION:An electron gun concerned is composed of a cathode 1, a heater 2 to heat it, a convergence electrode 3 adjacent to the cathode 1 and positioned apart therefrom coaxially, an anode 4 confronting the cathode 1 and electrode 3 and positioned apart therefrom coaxially, and a high frequency circuit part 5 arranged in the axial direction on the same axis as the anode 4. A conical projection 9 as an electron beam checking member made of a material having a heat resistance and having a small work function such as Mo, Ta. ceramic is installed anew at the center of the cathode 1 and is coupled with a cathode base 10 through a brazed layer 15. The projection 9 is coated with carbon, SiC, MO2B, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a straight beam microwave tube electron gun used for amplification of microwaves in a straight beam microwave tube represented by a klystron or a traveling wave tube.

[0002]

2. Description of the Related Art FIG. 6 is a sectional view showing an electron gun of a conventional straight beam microwave tube disclosed in, for example, Japanese Patent Laid-Open No. 63-10430, in which 1 is a cathode and 2 is a cathode 1. A heater 3 for heating is provided with a focusing electrode 3 which is adjacent to the cathode 1 and is coaxially arranged apart therefrom, and 4 is an anode which is opposed to the cathode 1 and the focusing electrode 3 and is coaxially arranged apart therefrom. Reference numeral 5 is a high-frequency circuit portion arranged coaxially with the anode 4 in the axial direction. 7 (a) and 7 (b) are electron beam trajectories by computer simulation in such a conventional electron gun.

Next, the operation will be described. First, the heater 1 is heated to raise the temperature of the cathode 1 to emit an electron beam from the cathode, and a high voltage is applied to the anode 4 to extract the accelerated electron beam. At this time, the electron beam shape, which is the electron beam amount, is determined while the voltage of the focusing electrode 3 is suppressed. That is,
By applying a negative potential to the focusing electrode 3, the electron beam is not emitted from the outer peripheral portion of the cathode 1 and the emission amount from the central portion is reduced. This state is called cutoff, and a normal electron beam is not formed, but an electron beam parallel to the axis at the center of the axis is incident on the high frequency circuit section 5.

A simulation diagram of the flow of the electron beam when the focusing electrode 3 is turned on and cut off by controlling the potential is as shown in FIGS. 7 (a) and 7 (b). According to this, the cathode 1 is, for example, 1050 ° C.
It is heated to a certain degree, and thermoelectrons are emitted from the surface of the cathode 1. At this time, the potential of the cathode 1 is −9.2 KV, the potential between the anode and the ground is 0 V, and the focusing electrode 3 is at substantially the same potential as the cathode 1. .

At this time, an electric field R is formed by the cathode 1, the anode 4, and the focusing electrode 3, and the operation is like an electron lens. That is, the electrons E emitted from the cathode 1 form a smooth flow bundle so as to be substantially orthogonal to the equipotential lines of the electric field (R), as shown in FIG.
Enters into the center hole of and enters the high frequency circuit section 5. Microwaves are input to the high frequency circuit 5, and the microwaves are amplified by the interaction between the high frequency and the electron beam.

On the other hand, at the time of the cutoff, the focusing electrode 3
Is given a negative potential when viewed from the cathode 1,
Although it depends on the potential level, the amount of electrons emitted from the cathode 1 is suppressed. Therefore, the suppression effect is not so great in the central part except the cathode peripheral part, and some electrons hit the anode 4 and do not enter the high frequency circuit part 5 as shown in FIG. Matching electrons are radiated, a part of them is accelerated by the anode, amplification is performed in the high frequency circuit section 5, and noise is generated.

[0007]

Since the conventional electron beam gun of the straight beam microwave tube is constructed as described above,
The electron beam current when the electron beam is cut off by the focusing electrode 3 is inevitably large, and each part of the electron gun is exposed to high temperature, and noise is generated when part of the electron beam enters the high frequency circuit part 5. There was such a problem.

The invention according to claim 1 is made to solve the above-mentioned problems. The electron beam current at the time of cutoff of the electron beam is reduced and the electron beam is incident on the high frequency circuit. The aim is to obtain an electron gun with a straight beam microwave tube that can be prevented.

Another object of the present invention is to provide an electron gun of a straight beam microwave tube in which an electron beam blocking member can be easily and surely integrated with a cathode base.

A third object of the present invention is to provide an electron gun of a straight beam microwave tube which can surely prevent the emission of an electron beam from the central portion of the cathode.

[0011]

In the electron gun of the straight beam microwave tube according to the invention of claim 1, the electron beam blocking member for blocking the emission of the electron beam from the central portion of the cathode is provided in the cathode. It is a thing.

An electron gun of a straight-beam microwave tube according to the present invention of claim 2 is mounted on the cathode base for emitting an electron beam and the cathode base by brazing or welding so that the central portion of the cathode base is removed. An electron gun is composed of an electron beam blocking member that blocks the emission of an electron beam.

According to the third aspect of the present invention, the cathode is composed of an electron beam blocking member for blocking the emission of the electron beam from the central portion of the cathode and an electron emission suppressing material layer coated on the electron beam blocking member. Is.

[0014]

The electron beam blocking member according to the first aspect of the present invention blocks the emission of the electron beam from the central portion of the cathode, and when the electron beam is cut off by the focusing electrode, the electron beam is pushed down to the central axis side and the reaction is stopped. Bounces and blocks input to the high frequency circuit.

The electron beam blocking member according to the invention of claim 2 can be easily attached to the central portion of the cathode base by a joining operation such as welding.

The electron emission suppressing material layer according to the third aspect of the present invention surely blocks the emission of the electron beam through the electron beam blocking member.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a cathode, 2 is a heater for heating the cathode 1, 3 is a focusing electrode which is adjacent to the cathode 1 and is coaxially arranged apart therefrom, and 4 is a cathode 1 and a focusing electrode 3 which are opposed to each other. Anodes 5 and 5 are coaxially arranged apart from each other, and are high-frequency circuit portions coaxially arranged with respect to the anode 4.

Reference numeral 9 denotes a conical projection, which is disposed in the central portion of the cathode 1 and serves as an electron beam blocking member made of a material having heat resistance and a small work function, such as molybdenum, tantalum, or ceramic. The ring-shaped cathode base that constitutes the
And the cathode base 10 is bonded via a brazing layer 15, as shown in FIG. And the focusing electrode 3
The trajectories of the electron beam at the time of turning on and at the time of cutting off by the potential control of are as shown in the simulation diagram of FIG.

Next, the operation will be described. First, the cathode 2 is heated to a high temperature by heating the heater 2, and a high voltage is applied to the anode 4, whereby an electron beam is extracted, and the electron beam is emitted under the voltage control of the focusing electrode and the shape of the conical projection 9. The shape is decided. At this time, since there is a conical projection 9 in the center of the cathode 1,
Electrons are no longer emitted from the center of the cathode 1, and when turned on, the flow of the electron beam is smooth as shown in FIG. 3 (a) and is effectively input to the high-frequency circuit section 5, but at cutoff, FIG. 3 (b). As shown in, the electron beam is pushed down toward the central axis, which recoils the electron and disturbs the electron beam.

As a result, the electron beam does not enter the high frequency circuit section 5, and the amplification of the microwave is ultimately suppressed to 0, for example. That is, by cutting the input of the electron beam to the high frequency circuit section 5 in this way, it is possible to prevent noise from being generated.

FIG. 4 shows an electron gun structure according to a second aspect of the present invention. In the figure, 10 is a disk-shaped cathode base whose upper surface is recessed in an arc shape, and 9 is installed in the center of the cathode base 10. The conical protrusions 11 are a plurality of supports continuously provided on the outer periphery of the conical protrusions 9. By welding the supports 11 to the outer periphery of the cathode base 10, the conical protrusions 9 are formed. Stable on top of 10. In this embodiment, electron emission from the center of the cathode 1 can be suppressed in the same manner as described above, and attachment of the conical projection 9 to the center of the cathode base 10 by welding or the like can be facilitated.

FIG. 5 shows an electron gun structure according to the invention of claim 3, 9 is a conical projection mounted on the cathode base 10, and 12 is an electron emission coated on the surface (outer surface) of the conical projection 9. It is a suppressor layer. Further, as the electron emission suppressing substance, carbon, SiC, MO ₂
A heat resistant material such as B is used. According to this embodiment, the electron emission suppressing material layer 12 can more effectively suppress the emission of the electron beam from the central portion of the cathode, and the cathode material is formed on the surface of the electron emission suppressing material layer 12. Even if is attached, the emission of the electron beam can be suppressed.

[0023]

As described above, according to the first aspect of the present invention, the cathode is provided with the electron beam blocking member for blocking the emission of the electron beam from the central portion of the cathode. There is an effect that the input of the electron beam to the high-frequency circuit section at the time of cutoff can be suppressed and the generation of noise can be prevented without losing the characteristics of the electron beam.

According to the second aspect of the present invention, the cathode base for emitting the electron beam and the cathode base are attached to the cathode base by brazing or welding to prevent emission of the electron beam from the central portion of the cathode base. Since the electron gun is composed of the electron beam blocking member, there is an effect that the work of assembling the cathode can be performed easily and quickly.

Further, according to the third aspect of the present invention, the cathode is formed from the electron beam blocking member for blocking the emission of the electron beam from the central portion of the cathode and the electron emission suppressing material layer coated on the electron beam blocking member. Since it is configured, the emission of the electron beam at the central portion of the cathode can be blocked more reliably, and thus, the effect that noise generation in the high frequency circuit section can be sufficiently prevented is obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an electron gun of a straight beam microwave tube according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of the cathode in FIG.

FIG. 3 is a simulation diagram showing an electron beam trajectory in the present invention.

FIG. 4 is an enlarged sectional view of a cathode according to the invention of claim 2;

FIG. 5 is an enlarged sectional view of a cathode according to the invention of claim 3;

FIG. 6 is a sectional view showing an electron gun of a conventional straight beam microwave tube.

7 is a simulation diagram showing an electron beam trajectory according to FIG.

[Explanation of symbols]

1 cathode 3 Focusing electrode 4 anode 5 High frequency circuit 9 Conical projection (electron beam blocking member) 10 cathode base 12 Electron emission suppression material layer

Claims (3)

[Claims] 1. A cathode that emits an electron beam by heating a heater, a focusing electrode that determines the shape of the electron beam from the cathode by potential adjustment, and a center hole that is provided axially away from the focusing electrode. In an electron gun of a straight beam microwave tube having an anode that accelerates the electron beam passing therethrough and enters the high frequency circuit section, an electron beam that blocks emission of the electron beam from the central portion of the cathode to the cathode. An electron gun of a straight beam microwave tube, which is provided with a blocking member. 2. A cathode that emits an electron beam by heating a heater, a focusing electrode that determines the shape of the electron beam from the cathode by adjusting the potential, and a center hole that is provided axially away from the focusing electrode. In a straight-beam microwave tube electron gun including an anode that accelerates the electron beam passing therethrough and enters the high-frequency circuit section, a cathode base that emits the electron beam from the cathode and a brazing or brazing method to the cathode base. An electron gun for a straight-beam microwave tube, comprising an electron beam blocking member attached by welding to block emission of an electron beam from the central portion of the cathode base. 3. A cathode that emits an electron beam by heating a heater, a focusing electrode that determines the shape of the electron beam from the cathode by adjusting the potential, and a center hole that is provided axially away from the focusing electrode. In an electron gun of a straight beam microwave tube equipped with an anode for accelerating the electron beam passing therethrough and entering the high frequency circuit part, electron beam blocking for blocking the emission of the electron beam from the cathode to the cathode An electron gun for a rectilinear beam microwave tube comprising a member and an electron emission suppressing material layer coated on the electron beam blocking member.