JPS6219017B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radiation-cooled multistage collector for a traveling wave tube that has an enhanced effect of suppressing retrograde electrons.

In general, especially high-power traveling wave tubes mounted on artificial satellites are strongly required to improve efficiency in order to reduce power consumption and the amount of heat generated in the collector.

As one method for improving this efficiency, lowering the collector potential using a multi-stage collector is widely used.
This is an attempt to improve the efficiency of the traveling wave tube by capturing the electrons in the electron beam that have completed their amplification and are incident on the collector using multiple collector electrodes with different potentials, with as little heat loss as possible depending on their speed. It is something to do. However, the electric field created by the potential-dropping collector becomes a decelerating field for electrons incident on the collector, and an accelerating field for electrons traveling in the opposite direction, so that the electrons incident on the collector are not captured by the collector electrode. Secondary electrons emitted from the collector electrode may be captured by the high-potential collector electrode, or may be returned to the slow-wave circuit. This generates heat in the slow-wave circuit, which is sensitive to heat, and causes a disturbance in the normal operation of the traveling-wave tube and a decrease in efficiency.

Therefore, it is necessary to suppress these retrograde electrons.

FIG. 1 shows a cross-sectional view of a conventional radiation-cooled multi-stage collector designed to suppress retrograde electrons.
A vacuum envelope of the collector is formed by a support plate 2 connected to the end of the slow wave circuit 1, a bellows 3 made of a metal with low thermal conductivity (for example, stainless steel), and a collector can 4 which is a cylindrical metal container. A plurality of collector electrodes (four in this example), that is, first to fourth collector electrodes 5 to 8, are arranged inside the collector electrode. Note that the support structure for the first to fourth collector electrodes is not shown in the figure to simplify the drawing. First to third collector electrodes 5 to 7
is in the shape of a conical horn, and the fourth collector electrode 8 is in the shape of a cage. In such a configuration, between the slow wave circuit voltage V _B and the first to fourth collector electrode voltages V _C1 to V _C4, V _B >V _C1 >V _C2 >V _C3 >
When a voltage related to V _C4 is applied, the electrons with the slowest speed will move to the first collector electrode, the electrons with the fastest speed will move to the fourth collector electrode, and the electrons with intermediate speed will move to the second or third collector electrode as shown in electron trajectory 9. incident on . Since the electron incident surfaces of the first to third collector electrodes face the low potential electrode, the emitted secondary electrons are pushed back to the original electrode and are difficult to reach the high potential collector electrode or the slow wave circuit. However, a minimum point of potential occurs inside the fourth collector electrode, and an equipotential surface 10 is formed near the entrance of the fourth collector electrode, so that some of the secondary electrons and incident electrons emitted from the fourth collector electrode There is a drawback that the incident trajectory to the collector is likely to be pushed in the opposite direction, ie, back toward the slow wave circuit, by the force due to the electric field of the equipotential surface 10.

In order to eliminate this drawback of the example of FIG. 1, the arrangement shown in FIG. 2 has been considered. In this case, the fourth collector electrode of the example shown in FIG. 1 is divided into two parts, and a fourth collector electrode 11 in the shape of a conical horn and a fifth collector electrode 12 having a protrusion in the center are provided. In such a configuration, if the fifth collector electrode voltage V _C5 is lower than the fourth collector electrode voltage V _C4 , the equipotential surface near the entrance of the fourth collector electrode becomes 13. Therefore, a divergent force in the radial direction is applied to the incident electrons, and a radial force is also applied to the retrograde electrons, so that retrograde movement in the direction of the slow wave circuit can be suppressed.

Furthermore, as another method to suppress retrograde electrons,
In order to suppress the emission of secondary electrons, which are one of the sources of retrograde electrons, materials with low secondary electron emission, such as graphite, may be coated on the electron incident surface of the collector electrode, or the collector electrode may be formed from graphite itself. There are known ways to do this.

However, even the conventional multi-stage collector as described above has not been able to sufficiently suppress retrograde electrons. For example, it has been difficult to prevent secondary electrons emitted by electrons incident on the tip of the entrance of each collector electrode from moving backwards. Further, the emission of secondary electrons, which are part of the source of retrograde electrons, could not be completely eliminated even if a material with low secondary electron emission was used.

An object of the present invention is to provide a multistage collector that can suppress retrograde electrons that could not be suppressed by the conventional methods as described above.

This invention applies a magnetic field having a component in the direction perpendicular to the central axis of the collector, that is, in the radial direction, to change the traveling direction of retrograde electrons to the radial direction, thereby preventing the retrograde electrons from moving back toward the high-potential collector electrode or slow-wave circuit. It is something to suppress.

By the way, as a method of applying such a magnetic field, in the case of a conduction-cooled collector, a method of attaching a permanent magnet to an appropriate position on the outer surface of the collector is known. However, this same method cannot be used with radiation cooled collectors. This is because in a radiation-cooled collector, the surface of the collector can reaches a high temperature of 200 to 300 degrees Celsius during operation, so when a permanent magnet is attached to the surface of the collector can, the magnetic properties of the permanent magnet are affected by the temperature. This is because stable operation becomes impossible. The object of the present invention is to provide a radiation-cooled multi-stage collector that does not have these drawbacks.

Embodiments of the present invention will be described below based on the drawings. FIG. 3 shows a first embodiment of the present invention, in which a permanent magnet 14 is attached on the support plate 2 in addition to the one shown in FIG. It has been established. This rod-shaped body 17 penetrates the support body 2 from the outside of the vacuum envelope, one end of which extends close to the first collector electrode 5, and one end of the permanent magnet 14 is attached to the other end of the rod-shaped body 17 outside the vacuum envelope. The magnetic poles are touching. In FIG. 3, the same reference numerals as in FIG. 1 represent the same parts. Furthermore, outside the slow wave circuit 1, there are many permanent magnets 1 that create a periodic magnetic field for converging the electron beam.
5 is included.

In such a radiation-cooled multistage collector, the first
The heat generated at the fourth collector electrodes 5 to 8 is transmitted to the collector can 4 by radiation and conduction, and is radiated from the surface of the collector can 4 into the surrounding space. Collector can 4 and support plate 2
are insulated by a bellows 3 made of a metal with low thermal conductivity, and also by an insulating structure (not shown) between the first to fourth collector electrodes 5 to 8 and the support plate 2. ing. The surface of collector can 4 is heated to 200℃ or more during traveling wave tube operation.
The temperature reaches 300℃. Therefore, the first idea of this idea is
In this embodiment, since the permanent magnet 14 is mounted on the support plate 2 which is at a low temperature on the slow wave circuit side, there is no problem that the magnetic properties of the permanent magnet 14 are affected by temperature.

In this configuration, the N pole and S pole of the permanent magnet 14
When the poles are arranged as shown in the figure, a magnetic flux 16 is generated within the collector, and a magnetic field having a radial component is created on the electron orbit. Therefore, the traveling direction of the retrograde electrons is bent in the radial direction by this radial magnetic field, and the retrograde movement is suppressed.

FIG. 4 shows a second embodiment of the present invention, in which the rod-shaped body 17 of the first embodiment is placed between the collector can 4 and the first to fourth collector electrodes 5 to 8 inside a vacuum envelope. It is expanded in between.

According to this configuration, a magnetic flux 16 is generated within the collector, and the same operation and effect as in the first embodiment can be obtained. Furthermore, since the magnetic field strength in the deep part of the collector is stronger than that in the first embodiment, it is possible to effectively suppress electrons moving backward in the deep part of the collector. This effect is due to the rod-shaped body 17
If the tip of the collector is shaped like the tip of a shiyamoji to increase its surface area, the strength of the magnetic field at the back of the collector will become stronger, making it even more effective.

As is clear from the above description, according to the present invention, retrograde electrons that could not be suppressed by conventional methods can be suppressed. Moreover, since the temperature of the permanent magnet that creates the magnetic field for suppressing retrograde electrons does not rise, the magnetic properties are not affected by temperature and stable operation is possible. By suppressing retrograde electrons in this way, the efficiency of the traveling wave tube can be improved. Furthermore, since the heat generated by the collector and slow wave circuit is reduced, the heat load on these components is reduced, and reliability can be expected to be improved.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of a conventional radiation-cooled multistage collector, and FIGS. 3 and 4 are partially cutaway cross-sections of a radiation-cooled multistage collector according to the first and second embodiments of the present invention. It is a diagram. DESCRIPTION OF SYMBOLS 1... Slow wave circuit, 2... Support plate, 3... Bellows, 4... Collector can, 5-8... First to fourth collector electrodes, 14... Permanent magnet, 16... Magnetic flux, 17 ...A rod-shaped body.

Claims (1)

[Claims] 1 A plurality of collector electrodes 5 to 8 are placed in a vacuum envelope formed by connecting a cylindrical metal container 4 serving as a radiant heat dissipation surface to a support plate 2 connected to a slow wave circuit section 1 via a low heat conduction member 3. In the radiation-cooled multi-stage collector of a traveling wave tube, a permanent magnet 14 is provided on the support plate 2 outside the vacuum envelope, and one end is in contact with one magnetic pole of the permanent magnet 14, and the other end is in contact with one magnetic pole of the permanent magnet 14. A radiation-cooled multi-stage collector of a traveling wave tube, characterized in that a rod-shaped body 17 made of ferromagnetic metal is provided which penetrates the support plate 2 and projects into the inside of the vacuum envelope.