JPH0216533B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in multi-cavity klystrons.

As is well known, a multi-cavity klystron has an electron gun section that emits an electron beam, a high frequency circuit section that causes the electron beam emitted from the electron gun section to interact with high frequency power, and a high frequency circuit section that generates high frequency power in the high frequency circuit section. A collector section that captures the electron beam that has finished interacting with the electric power and converts it into thermal energy, focuses the electron beam emitted from the electron gun section, and generates a magnetic field that allows the electron beam to pass through the high-frequency circuit section. It consists of a focusing device, etc. Among these, the high frequency circuit section usually consists of 4 to 6 resonant cavities, a tuner mechanism for varying the resonant frequency of the resonant cavities, and a coupling section with an input/output circuit, and the coupling with the input circuit is the most The input cavity is a resonant cavity on the electron gun side, and the coupling with the output circuit is performed in the output cavity, which is a resonant cavity located closest to the collector side. Further, the focusing device is composed of an electromagnet or a permanent magnet, and magnetic pole pieces of an input section and an output section placed at both ends of the high frequency circuit section for leaking a magnetic field into the high frequency circuit.

For multi-cavity klystrons with a relatively low output of around 3 kW or less, permanent magnets are used because the electron beam can be focused with a relatively weak magnetic field due to the miniaturization of the entire klystron and ease of operation. A focusing device is used.

FIG. 1 shows an example of a multi-cavity klystron using a conventional permanent magnet focusing device. In Figure 1, 1 is an electron gun section that generates an electron beam, 2 is a high-frequency circuit section, 3 is a collector section that captures the electron beam and converts it into thermal energy, 4 is a permanent magnet, 5 is a yoke, and 6 is an input 7 is the output pole piece,
8 is an input circuit, 9 is an output circuit, 10 is a resonant cavity constituting a high frequency circuit, and 11 is a drift tube for an electron beam path. FIG. 1 shows a case where the input circuit 8 is a coaxial line and the output circuit 9 is a waveguide.

Now, in FIG. 1, the strength of the magnetic field created by the permanent magnet 4 is determined by the magnitude of the electron beam current passing through the high-frequency circuit, the diameter of the electron beam when passing through the drift tube 11, the input magnetic pole piece 6 and the output. It is determined by the length lg between the magnetic pole pieces 7, the facing area Sg between the magnetic pole pieces 6 and 7, and the like. The larger the electron beam current and the smaller the electron beam diameter, the stronger the magnetic field needs to be, so the permanent magnet 4 needs to be larger or made of a magnetic material that can produce a strong magnetic field. . If the distance lg between the magnetic pole pieces 6 and 7 becomes longer, the length lm of the permanent magnet 4 should normally be longer in proportion to lg in order to obtain the magnetic field necessary to pass the electron beam through the high-frequency circuit. It becomes necessary. However, the distance lg between the input and output magnetic pole pieces 6 and 7 is determined by the maximum output required for the multi-cavity klystron, the available bandwidth, and the length of the high-frequency circuit section by the electron beam voltage and current. It cannot be made any shorter than necessary for storage purposes.

Further, the magnet cross-sectional area Sm needs to be large enough to pass the magnetic flux generated by the magnet 4 without saturating it.
In addition, in order to effectively obtain a magnetic field distribution between the input and output magnetic pole pieces 6 and 7, a certain amount of magnetic pole piece facing area Sg is required, and normally the larger Sg, the larger the magnet cross-sectional area Sm.
A large magnet is also required, and the cross-sectional area of the magnet cannot be made smaller than necessary.

In this way, the permanent magnet 4 of the multi-cavity klystron
The size of the permanent magnet 4 is almost determined by the strength of the magnetic field required for focusing the electron beam, the length of the high frequency circuit section, and the material of the permanent magnet 4. Furthermore, the larger the permanent magnet 4 becomes, the larger the yoke portion 5 that connects the upper and lower permanent magnets needs to pass through, so it is necessary to have a large cross-sectional area. Therefore, if the distance between the magnetic pole pieces 6 and 7 of the input/output section can be shortened without changing the shape of the high frequency circuit section, this can be an effective means for downsizing the permanent magnet.

The present invention provides a multi-cavity klystron that solves the above problems.

FIGS. 2 and 3 show an embodiment of a multi-cavity klystron employing the present invention. Similar to Figure 1,
1 is an electron gun section, 2 is a high frequency circuit section, 3 is a collector section, 4 is a permanent magnet, 5 is a yoke, 6 is an input section magnetic pole piece, 7 is an output section magnetic pole piece, 8 is an input circuit, 9 is an output circuit, 10 is a resonant cavity, and 11 is a drift tube. The difference in FIG. 2 from FIG. 1 is that the portion of the input magnetic pole piece 6 facing the output magnetic pole piece 7 forms the cavity wall of the input resonant cavity. Also the third
In the figure, the facing portion of the output pole piece 7 also serves as the cavity wall of the output resonant cavity. As a result, in Fig. 1, the gap distance lg between the input part magnetic pole piece 6 and the output part magnetic pole piece 7 constitutes the resonant cavity of the input part or output part in Fig. 2 or 3. The thickness of the conductor plate is reduced by Δlg, and the gap distance becomes lg - Δlg. Taking the example of a multi-cavity klystron with five cavities in the 6 GHz band, the distance lg between the magnetic pole pieces 6 and 7 is approximately 65 mm, and the thickness of the plate separating the resonant cavities and the magnetic pole pieces 6 and 7 of the input and output cavities are approximately 65 mm. The thickness Δlg of the cavity wall between 7 and 7 is about 2.5 mm, and if the present invention is adopted, the gap, distance lg−Δlg=
It becomes 62.5mm, which is a decrease in gap distance of about 4%. This directly means that the length lm of permanent magnet 4 is 4
% shorter, it is possible to create an equivalent magnetic field in the high frequency circuit section 2 in the gap. Furthermore, if the gap length between the magnetic pole pieces 6 and 7 is shortened,
Since unnecessary magnetic field leakage to other parts is reduced accordingly, it is possible to reduce the cross-sectional area of the magnet 4 and shorten the length of the magnet 4 to lm - Δlm.
Furthermore, since it is possible to reduce the total magnetic flux generated by the magnet 4, it is also possible to reduce the cross-sectional area of the yoke part 5, and as a result, the permanent magnet 4 and the yoke part 5 can be reduced.
With the klystron structure shown in Figures 2 or 3, the combined weight reduction can be close to 10%.

In addition, the structures shown in FIGS. 2 and 3 are combined, and the cavity walls on the electron gun 1 side and the collector 3 side of the input resonant cavity and the output resonant cavity, respectively, are used as the magnetic pole pieces of the input part and the output part. The distance between the magnetic pole pieces is lg−
2Δlg, which reduces the gap length by about 8%, which ultimately makes it possible to reduce the weight of the permanent magnet device by about 20%. The explanation has been given using the numerical values for a five-cavity klystron in the 6 GHz band as an example, but it goes without saying that similar results can be obtained for multi-cavity klystrons in other frequency bands.

As described above, in the multi-cavity klystron that adopts the present invention, it is possible to significantly reduce the weight of the permanent magnet focusing device, which makes the multi-cavity klystron easier to handle and reduces manufacturing costs. be.

It goes without saying that the scope of multi-cavity klystrons employing the present invention includes those in which the surfaces of the input or output magnetic pole pieces are plated with Cu or the like.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the structure of an example of a conventional multi-cavity klystron, and FIGS. 2 and 3 are cross-sectional views showing the structure of a multi-cavity klystron employing the present invention. 1... Electron gun section, 2... High frequency circuit section, 3...
Collector, 4...Permanent magnet, 5...Yoke, 6...
...Input pole piece, 7...Output pole piece, 8...Input circuit, 9...Output circuit, 10...Resonance cavity, 1
1...Drift tube.

Claims (1)

[Claims] 1. An electron gun section that generates an electron beam, a high frequency circuit section that causes the electron beam generated from the electron gun section to interact with high frequency power, and an electron beam that has finished interacting with the high frequency power in the high frequency circuit section. In the multi-cavity klystron, the high-frequency circuit section is composed of a plurality of resonant cavities, and the high-frequency circuit section is composed of a collector section that captures electron beams and converts them into thermal energy, and a permanent magnet that creates a magnetic field for focusing the electron beam. A multi-cavity klystron characterized in that a part or the entire cavity wall of at least one of an input resonant cavity and an output resonant cavity among the resonant cavities is made of a magnetic material.