JPS6110936B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a straight beam type multi-cavity klystron using permanent magnets as a beam concentrator.

This type of multi-cavity klystron is shown in Figure 1a,
As shown in FIG. 1B, an example is shown in Fig. 1, an electron gun section 1 that generates an electron beam, a high frequency circuit section 2 that amplifies high frequency power using the energy of the electron beam, a collector 3 that captures the electron beam, and a focusing magnetic field device (electron gun section). The main components include a side magnetic pole piece 4, a collector side magnetic pole piece 5, an electron gun side permanent magnet 6, a collector side permanent magnet 7, and a yoke 8 stretched between the permanent magnets 6 and 7. Because they are small, lightweight, and have high electrical performance, they have come to be widely used in a variety of applications. However, in the case of klystrons that operate at high frequencies of GHz or higher, the operation of the klystron often becomes unstable or the electron beam intensively overheats the lower part of the collector. To solve these problems, there is a method to improve the unstable operation of the klystron by making the collector with a ferromagnetic material to improve magnetic shielding and prevent electrons from going backwards from the collector to the high frequency circuit, or to improve the unstable operation of the klystron. There have been methods to improve the cooling effect of the collector by increasing its thickness, but in the former case there remains a problem with the heat dissipation effect, and in the latter case there are disadvantages such as high material costs and increased weight.

Therefore, in FIG. 1, the magnetic pole piece 5 on the collector side is made thinner to achieve appropriate magnetic saturation, and the beam is refocused within the collector by partially exposing the magnetic pole end surface of the magnet 7 to which the magnetic pole piece 5 is connected. There is a proposal for a method of forming a leakage magnetic field to cause the electron beam to collide with the upper part of the collector. It was found that by this means, the unstable operation of the klystron and the local overheating near the collector inlet were improved. However, when this method is actually applied, the trajectory of the beam within the collector changes considerably due to variations in the strength of the magnetic field of the permanent magnet, variations in the structure of the electron gun, or variations in the characteristics of the high-frequency circuit. It was found that in some cases, the beam could centrally heat the top of the collector. For this reason, it is necessary to correct the degree of saturation of the magnetic poles for each sphere in accordance with the above-mentioned various variations so that the beam disperses and heats the upper part of the collector. However, since the magnetic pole piece 5 also serves as the vacuum vessel of the klystron,
After the klystron was developed, adjusting the saturation of the magnetic pole pieces was extremely difficult in practice, and its practical use was quite limited.

The present invention eliminates the above-mentioned disadvantages and provides a klystron having a structure in which the amount of leakage magnetic field in the collector region can be freely controlled from the outside after the klystron is completed.

A klystron according to the invention is shown in FIG.
In FIG. 2, a plate-shaped ferromagnetic member 9 is stacked on the side surface of the collector-side permanent magnet 7.
An example of actual measurements of leakage magnetic fields showing the effect of the ferromagnetic member 9 is shown in FIG. In FIG. 3, the horizontal axis represents the distance Z along the central axis of the klystron, and the vertical axis represents the magnetic flux density B. Curve 11 is the case when there is no ferromagnetic member, curve 12 is the case when a relatively thin member is used, and curve 13 is the case when a relatively thick member is used. In this way, it was confirmed that the leakage magnetic field in the collector region can be freely controlled from the outside by changing the thickness of the member. Furthermore, it has been found that the leakage magnetic field can be adjusted by keeping the thickness of the member 9 constant and changing the size of the member and its position on the permanent magnet.

In Figure 4, the horizontal axis is the accelerating voltage E of the klystron.
_B This is an example in which the effect of the ferromagnetic member 9 on the collector temperature rise, with the temperature rise ΔT plotted on the vertical axis, was measured. When the member 9 is not present, as shown in FIG. 4a, the value of the temperature rise at the collector apex point B is higher than at the point A on the side surface near the base of the heat dissipation blade 10 of the collector 3 shown in FIG. This shows that the collision mainly occurs at the top of the collector. When a suitable member 9 is placed, the temperature at point A will rise slightly and the temperature at point B will fall, as shown in Figure 4b.
This shows that the temperature is well balanced.

Furthermore, the ferromagnetic members 9 on the four sides of the collector-side magnet are arranged slightly asymmetrically with respect to the central axis of the klystron, making the leakage magnetic field inside the collector asymmetrical, thereby reducing the flow of electrons from the collector to the high-frequency circuit section. It was also confirmed that it is extremely effective in reducing the retrograde motion of the klystron and stabilizing the motion of the klystron.

As described above, in a klystron that uses a permanent magnet as a beam focusing device, by adding an appropriate ferromagnetic material to the side surface of the upper permanent magnet, the strength of the leakage magnetic field and biased magnetism in the collector region can be reduced from the outside. It has become possible to manufacture a klystron that can be freely adjusted, has extremely stable operation, and has good collector cooling efficiency, and its practical effects are extremely high.

[Brief explanation of the drawing]

Figure 1a is a vertical cross-sectional view along the axis showing an outline of the structure of a conventional klystron, and Figure 1b is a line A--A in Figure a.
It is a sectional view taken along arrow A. FIG. 2 is a longitudinal cross-sectional view of an embodiment of the present invention, FIG. 3 is a curve diagram showing the magnetic flux density distribution along the axis for explaining the effects of the present invention, and FIG. 4 a
4 is a curve diagram showing the collector temperature rise of the conventional klystron, and FIG. 4b is a curve diagram showing the collector temperature rise according to the present invention. In the figure, 1...electron gun section, 2...high frequency circuit section, 3...collector, 4...electron gun side magnetic pole piece,
5... Collector side magnetic pole piece, 6... Electron gun side permanent magnet, 7... Collector side permanent magnet, 8... Yoke,
9 shows a ferromagnetic member for adjusting leakage magnetic field, 10 shows a heat dissipation blade.

Claims (1)

[Claims] 1. In a straight beam type multi-cavity klystron equipped with a permanent magnet type beam focusing magnetic field device that generates a main magnetic field for electron beam focusing in the high frequency circuit section and a leakage magnetic field for electron beam refocusing in the collector region, A straight beam type multi-cavity klystron, characterized in that a ferromagnetic member for adjusting a leakage magnetic field is provided on a side surface of a collector-side magnet of the magnetic field device.