JPH0541171A - Linear beam microwave tube - Google Patents

Abstract

PURPOSE:To reduce the cost of a cathode by setting an electron emission surface of the cathode as an electron source for a linear beam microwave tube to be flat. CONSTITUTION:A cathode 1 is heated at 900-1100 deg.C by a heater 4, and electrons are emitted from an electron emission surface 6. These electrons are focused by a Wehnelt 2 to form an electron beam 5 accelerated by a high voltage applied to an anode 3 to be guided to a high frequency circuit part positioned on the downstream. The electron emission surface 6 of the cathode 1 is formed flat to set a motion direction of the electrons at an instant they jump from the cathode 1 is parallel to a tube axis. The electrons getting out of the flat- shaped electron emission surface 6 are focued to pass an anode 3 to be guided into a spiral 7 forming a high frequency circuit, so microwaves are amplified by mutual action with the microwaves existing on the spiral 7. The electrons passing the spiral 7 are caught by a collector 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear beam microwave tube such as a traveling wave tube used as a microwave amplifier, and more particularly to a cathode shape of an electron gun portion of the linear beam microwave tube.

[0002]

2. Description of the Related Art As is well known, a straight-beam microwave tube such as a traveling wave tube amplifies a microwave by an electron gun section that generates an electron stream and an interaction between the electron stream created by the electron gun and the microwave. It comprises a high frequency circuit part for performing the above, a collector part for capturing the electron flow passing through the high frequency circuit part and converting it into heat energy, a magnetic pole and a magnet for generating a magnetic field for converging the electron flow. As shown in FIG. 3, the electron gun portion includes a cathode 1 for emitting electrons, a heater 4 for heating the cathode 1, a Wehnelt 2 for focusing the electrons emitted from the cathode 1, and an electron acceleration. A Pierce-type electron gun including an anode 3 and the like is used.
Further, in this Pierce type electron gun for a linear beam microwave tube, in the high frequency circuit section which is usually constituted by a spiral or the like, the electron emission surface 6 of the cathode 1 has a curvature in order to obtain an electron flow 5 of a thin and large current. It has a spherical shape with its center located on the tube axis, the emitted electron flow is reasonably focused, passes through the central hole of the anode 3, and is guided to a high-frequency circuit section composed of a spiral located further downstream. Get burned. Thus, the pierce electron gun that produces the thin electron stream 5 from the large cathode 1 is called a focused pierce electron gun. An optimum value for the radius of curvature of the cathode 1 is determined from the focusing ratio of the electron flow 5, the acceleration potential of the anode 3, the current value of the electron flow 5, and the like.

[0003]

As described above, the electron emission surface 6 of the cathode 1 for emitting electrons of the linear beam microwave tube.
The shape of is a spherical shape. The processing of such a spherical shape is usually performed by using a lathe, but the processing cost becomes expensive because the curvature of the spherical surface requires extremely high accuracy. Further, since the spherical surface is processed by the lathe, the surface roughness is usually limited to about 5 μm, and the minute disturbance of the electron orbit due to this surface roughness becomes noise of the linear beam microwave tube and adversely affects the characteristics. Is affecting.

Further, since the electron emission surface 6 has a spherical shape, the outermost diameter portion of the electron emission surface 6 has a knife edge shape especially when the radius of curvature of the spherical surface is small. There was a problem such as a cause of chipping of an edge during assembling.

[0005]

SUMMARY OF THE INVENTION According to the present invention, an electron gun section for generating an electron flow, a high frequency circuit section for interacting an electron flow with a microwave, and an electron stream after the interaction are captured to obtain thermal energy. In a linear beam microwave tube composed of a collector part for converting into an electron stream and a magnetic circuit for converging an electron flow, the electron emission surface 6 of the cathode 1 constituting the electron gun part which is the electron flow source is not a spherical surface as in the conventional case. It is characterized by being a plane.

[0006]

The present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an electron gun portion of a linear beam microwave tube according to an embodiment of the present invention. In FIG. 1, the cathode 1 is heated to 900 ° C. to 1100 ° C. by the heater 4, and electrons are emitted from its electron emission surface 6. The emitted electrons are focused by the Wehnelt 2 and are accelerated by the high voltage applied to the anode 3 to form an electron stream 5, which is guided to a high frequency circuit located further downstream by a so-called focused pierce electron gun. is there. Here, the electron emission surface 6 of the cathode 1 has a planar shape, and the movement direction of the electron at the moment when the electron jumps out from the cathode is parallel to the tube axis. However, due to the presence of the Wehnelt 2 which is a focusing electrode, the equipotential surface 14 has the shape shown in FIG. 1 in the space between the cathode 1 and the anode 3, and the electric field is in the direction perpendicular to the equipotential surface 14. The electrons emitted from the cathode receive a force of focusing in the direction of the electric field, pass through the central hole of the anode 3, and are guided to the high frequency circuit section. As described above, the shape of the electron emission surface 6 does not necessarily have to be a spherical surface, and even if it is a flat surface, the electrons are sufficiently focused and the required electron flow 5 can be formed.

As a result of various experiments, if the ratio of the diameter of the electron flow 5 to the outer diameter of the electron emission surface 6 of the cathode 1 is about 1: 3 or less, even if the shape of the electron emission surface 6 is flat. It is confirmed that there is almost no difference from the case of the spherical surface and the electrons are focused and the required electron flow 5 is obtained.

FIG. 2 is a longitudinal sectional view of an example of a spiral traveling wave tube which is a kind of the linear beam microwave tube according to the present invention. In FIG. 2, the electron emission surface 6 of the cathode 1 has a flat shape, and as described above, the electrons emitted from the cathode 1 are focused and passed through the anode 3, and then guided into the spiral 7 forming a high frequency circuit. Then, the microwave is amplified by the interaction with the microwave existing on the helix 7. Further, the electrons that have passed through the helix 7 are captured by the collector 10.

[0009]

As described above, the present invention is characterized in that the electron emission surface 6 of the cathode 1 which is the electron source of the linear beam microwave tube is flat, and as a result, the outer shape of the cathode 1 is processed. Can be facilitated. This makes it possible to reduce the cost of the cathode, which is one of the expensive parts of the linear beam microwave tube, and has the effect of reducing the cost of the linear beam microwave tube.

Further, by making the shape of the electron emission surface 6 of the cathode 1 to be a flat surface, the surface roughness of the electron emission surface 6 is conventionally cut by lathe when processing the spherical electron emission surface 6. Although there is a limit to this, by using a flat surface, it is possible to further improve the surface accuracy by lathing after polishing. This can eliminate the disturbance of the electron orbit due to the surface roughness of the electron emission surface 6, makes it possible to obtain the electron flow 5 having a good laminar flow property, and the characteristics such as noise of the linear beam microwave tube. It has the effect of improving.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a main electrode portion of an electron gun section of a linear beam microwave tube according to the present invention.

FIG. 2 is a vertical cross-sectional view of a spiral traveling wave tube which is an example of the linear beam microwave tube of the present invention.

FIG. 3 is a vertical cross-sectional view showing a main electrode portion of an electron gun section of a conventional linear beam microwave tube.

[Explanation of symbols]

 1 Cathode 2 Wehnelt 3 Anode 4 Heater 5 Electron flow 6 Electron emission surface 7 Helix 8 Magnetic pole 9 Magnet 10 Collector 11 Dielectric support rod 12 Input section 13 Output section 14 Equipotential surface

Claims (1)

[Claims] 1. An electron gun section for generating an electron stream, a high-frequency circuit section for interacting the electron stream with a microwave, a collector section for capturing the electron stream after the interaction and converting it into heat energy, and an electron. In a linear beam microwave tube including a magnetic circuit for focusing a flow, the electron gun unit is a focused pierce electron gun, and the electron emission surface of a cathode constituting the electron gun is a flat line. Beam microwave tube.