JPH0155537B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of the cavity of a linear multi-cavity klystron.

A linear multi-cavity klystron consists of an electron gun section that generates an electron beam, multiple cavities that perform high-frequency operation with the electron beam, an input and output coupling section that couples high-frequency power to the cavity, and an electron beam. The main components are a collector section that captures the electron beam, a magnetic field generator that focuses the electron beam, etc. Hereinafter, only the cavity portion according to the present invention will be described.

Examples of the cavity structure of a conventional linear klystron are shown in FIGS. 1 and 2a and 2b. First of all, referring to FIG. 1, 1 is an electron beam, 2 is a convex part that forms part of the drift tube and constitutes a high-frequency action gap, 3 is a cavity wall, 4 is a movable wall (also known as a guide plate),
5 is a bellows, 6 is a shaft, and 7 is a member connecting 5 and 6. In such a configuration, when the shaft 6 is moved in the direction a or b in the figure, the guide plate 4 moves integrally with the shaft 6 while contacting the cavity wall 3. When the shaft 6 moves in the direction a, the resonant frequency of the cavity decreases, and when the shaft 6 moves in the direction 6, the resonant frequency increases.

Next, referring to FIGS. 2a and 2b, the same symbols indicate the same parts as in FIG. 1, and numeral 8 indicates a capacitor plate having a crescent-shaped cross section. Also in this figure, the shaft 6 is moved in the c direction or the d direction shown in the figure. When the shaft 6 moves in the c direction, the resonant frequency of the cavity increases, and when the shaft 6 moves in the d direction, the resonant frequency decreases.
The method shown in FIG. 1 is called L tuning, and the method shown in FIG. 2 is called C tuning.

Now, the following problems can be considered in the cavity of the above-mentioned conventional structure. In the case of the L tuning method shown in FIG. 1, it is difficult to move the guide plate 4 with respect to the cavity wall 3 while maintaining electrical contact. Usually, fingers or springs are used for the contact part, but
As the power generated in the cavities increases, they may become thermally unsustainable. In the case of the C tuning method shown in Fig. 2, the capacitor plate 8 and convex portion 2 must be fairly close to each other in order to enhance the tuning effect.
If the power of the cavity is high, the problem of high frequency discharge between the two,
Alternatively, a problem arises in which the heat capacity of the capacitor plate 8 is insufficient. Furthermore, since the capacitor plate 8 having a crescent-shaped cross section can in principle have a shape that is only half or less of the circumference surrounding the working gap, a substantially large tuning effect cannot be expected.

In view of the above-mentioned drawbacks of conventional structures, it is an object of the present invention to provide a new type of cavity tuning scheme.

The structure of the cavity according to the invention is shown in FIGS. 3a and 3b. In Figure 3, 1 to 3 and 5 to 7 are the first
Figure 2 shows the same thing as Figure 2. 9 indicates a ring-shaped capacitor surrounding the working gap. e, f are shaft 6
Indicates the direction of movement of the right end. A point P shown at the center of the shaft indicates the position of the rotation center axis of the shaft when the right end of the shaft moves in directions e and f. In principle, it is desirable that this position be set approximately at the center of the bellows 5. In such a configuration,
When the shaft 6 moves in the f direction, the capacitor 9 is displaced as shown by the dotted line in the figure, so the tuning frequency of the cavity increases. Conversely, if the shaft 6 moves in the e direction, the tuned frequency will decrease.

The first feature of the present invention is that the capacitor plate is changed from the conventional crescent shape to a complete annular shape. The second feature is that the direction of displacement of the capacitive plate has been changed from the conventional direction perpendicular to the beam to essentially horizontal.

Next, the effects obtained when the present invention is implemented will be described. In the present invention, the opposing area between the capacitor plate and the protrusion 2 is increased by 2 to 5 times compared to the conventional one, so if other conditions are held constant, the distance between the capacitor plate and the protrusion 2 can be increased. High frequency discharge troubles are less likely to occur. Also, if the annular capacitor is made hollow,
Compared to the conventional three-moon structure, this has a great advantage in that the water cooling structure of the capacitor itself can be easily constructed. Furthermore, if the radial distance between the capacitor and the convex portion 2 is considered under constant conditions, the capacitance variable effect in the present invention is 2 to 5 times that of the conventional one, so even if the displacement of the capacitor is small, it is still better than the conventional one. This means that the same tuning range can be covered. This narrows the range of deformation of the bellows, thereby reducing the "swelling" caused by repeated use of the bellows over a long period of time, which helps improve the reliability of the bellows. It also becomes possible to change the frequency within a short period of time.

FIG. 3 shows the principle of the present invention,
Several modifications can be considered for its practical use. For example, a very simple capacitor can be obtained by simply rolling a copper pipe into a single layer or multiple layers and allowing water to pass through it. Of course, in this case, it is necessary to provide a reciprocating path for water inside the shaft 6 so that the water comes into contact with the capacitor. It is also obvious that a diaphragm 10 may be used in place of the bellows 5 as shown in FIG. In addition, by increasing the length of the bellows and moving the P point away from the action gap,
It is also conceivable to make the moving direction of the capacitor more parallel to the beam direction.

[Brief explanation of drawings]

1, 2a and 2b are views showing conventional cavity structures, and FIGS. 3a and 3b, and 4 are views showing cavity structures according to the present invention. 1...Electron beam, 2...Drift tube convex part, 3
...Cavity wall, 4...Guidance plate, 5...Bellows, 6
... Shaft, 7 ... Connection member, 8, 9 ... Capacity plate, 10 ... Diaphragm, P ... Shaft rotation center position.

Claims (1)

[Claims] 1. An annular capacitor surrounding the working gap of a cavity resonator is fixed to a part of the cavity wall by a bellows or a diaphragm via a shaft, and the capacitor is fixed at a certain point on the shaft. A cavity resonator for a klystron, characterized in that it is configured to be movable substantially along a beam axis with P as the center of rotation. 2. The cavity resonator for a klystron according to claim 1, wherein the point P is set approximately at the center of the bellows.