JPH0750135A - Multi-cavity klystron - Google Patents

Abstract

PURPOSE:To make an electric field distribution non-uniform due to the effect of a waveguide uniform, by offsetting a cavity and a drift tube, in the input/ output cavity of a multicavity klystron. CONSTITUTION:In the input or output cavity 1 of a multicavity klystron, the center of a cavity and the center 7 of a drift tube are displaced to manufacture a cavity. At the time, a cavity appropriately interacting with an electron beam is provided by choosing an offset level 9 that enables to make a non-uniform electric field distribution caused by the effect of a waveguide 6, uniform, in the cavity, uniform.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to multicavity klystrons and, more particularly, to the structure of the output cavity used to extract microwave power.

[0002]

2. Description of the Related Art Multi-cavity klystrons are used in the fields of communications, industrial heating, particle accelerators and the like. Figure 7
8 shows a cross section of the output cavity portion of such a multi-cavity klystron, and FIG. 8 shows the output cavity 1 as A- in FIG.
It is cut three-dimensionally along the A'section. In the output cavity 1 of the multi-cavity klystron, the electrons 4 passing through the drift tube 2 interact with the high frequency electric field generated inside the cavity.

The electrons 4 entering the cavity are decelerated by the electric field 3 protruding into the cavity as shown in FIG.
The lost kinetic energy is converted into electromagnetic field energy in the cavity. FIG. 10 shows a magnetic field pattern when the cavity is cut along a plane perpendicular to FIG. Magnetic field 5 generated inside the cavity
The vortex causes a new magnetic field in the waveguide 6 coupled to the output cavity 1, and microwave energy is extracted from the waveguide 6 to the outside.

Therefore, in order to efficiently extract the energy of the electromagnetic field from the electrons 4 passing through the drift tube 2, a deceleration electric field matching the energy of the incident electrons 4 is generated in the output cavity 1, and It is important to optimize the coupling between the output cavity 1 and the waveguide 6.

[0005]

In order to convert the energy of the electron beam into the electromagnetic field energy in the cavity, as described in the section of the prior art, a deceleration electric field suitable for the energy of the incident electron beam is vacated. It needs to be generated inside the torso.

The axial electric field distribution generated inside the cavity is as shown in FIG. The A direction in FIG. 11 is the waveguide direction, and the central portion of the cavity also has a strong electric field. However, the electric field at the center of the cavity is biased toward the waveguide side from the center (P _{1 in} FIG. 11) on the opposite side (FIG. 1).
The electric field is stronger than that of P ₂ ).

FIG. 12 shows the electric field distribution in a cross section passing through the center of the cavity and P ₁ and P ₂ in FIG. As is clear from FIG. 12, the electric field strength of P ₁ is higher than that of P ₂ , and the electric field distribution is nonuniform. On the other hand, FIG. 13 shows the electric field distribution on a plane perpendicular to FIG. 12 and passing through the center of the cavity. in this case,
The peak of the electric field has a uniform height. The nonuniformity of the electric field shown in FIG. 12 is an influence of the waveguide 6 provided for extracting microwave power from the cavity, and is a problem that is always present in the input and output cavities 1 of the multicavity klystron. .

When the electric field distribution is nonuniform as described above, even if an ideal electron beam is incident on the output cavity, each electron interacts with a high electric field or a low electric field, so that a certain electron is necessary. As described above, when the energy of the electron beam is lost and the electron beam goes back to the electron gun side, or when the electron beam advances toward the collector without sufficient energy loss, there arise problems such as reduction in beam efficiency and heat generation in the collector section.

Further, in the case of a high power klystron used for a particle accelerator or the like, a non-uniform electric field inside the cavity causes a discharge or multipactor phenomenon inside the cavity, so that the cavity is destroyed. In some cases,

[0010]

SUMMARY OF THE INVENTION In the present invention, the center of the input or output cavity is opposite the waveguide with respect to the center of the drift tube in order to homogenize the non-uniform electric field inside the output cavity. Offset to the side.

The above-mentioned non-uniformity of the electric field is due to the influence of the waveguide installed for extracting the microwave power, and there is a method in which a total of two pairs of the waveguides for extracting the output are attached vertically symmetrically. , Not practical. For this reason, the mounting portion of the waveguide is offset from the center of the input or output cavity with respect to the central axis of the drift tube in order to obtain a uniform electric field inside the cavity, as in the conventional case.

[0012]

The present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of the present invention. As is clear from the drawing, the center 8 of the output cavity is offset from the center 7 of the drift tube to the opposite side of the waveguide 6. FIG. 2 is a diagram for clarifying the positional relationship between the center 7 of the drift tube and the center 8 of the output cavity. Figure 3
4A and 4B show the electric field distribution in the axial direction generated inside the output cavity 1, and the electric field distributions cut through the center 7 of the drift tube in respective vertical planes are shown in FIGS. From FIG. 4, the electric field strength inside the cavity is substantially uniform by offsetting the center 7 of the drift tube and the center 8 of the output cavity. In FIG. 4, the positive side of the horizontal axis represents the distance to the waveguide side, and the negative side represents the distance in the opposite direction to the waveguide. The offset amount 9 is as shown in FIG.

In order to apply the present invention to the actual design of the output cavity of the klystron, the amount of offset is clarified.
In FIG. 6, the horizontal axis represents the offset amount (the ratio of the offset amount to the drift tube radius), and the vertical axis represents the ratio (E _P1 / E _P2 ) of the two peak electric fields shown in FIG. That is,
If the offset amount is selected at the point where E _P1 / E _P2 = 1.0, the two electric field peaks have the same height. From Fig. 6, assuming that the offset amount is 35% of the drift tube radius, E
_{Since P1} / E _P2 ≈1.0, a substantially uniform electric field distribution can be expected. The calculation results at this point are shown in FIGS. The calculation of the offset amount was performed for a cavity size of a drift tube radius of 4 mm, a cavity radius of 12 mm, a cavity gap of 3 mm, and an iris size of 6 × 14 mm.
In the actual design, it is necessary to select the amount of offset to be optimum depending on the coupling state between the cavity and the waveguide.

Although the embodiment shown here is an example of application to the output cavity of the multi-cavity klystron, the drift tube and the input cavity are offset by the same method for the input cavity as well. A uniform electric field can be created inside the body.

[0015]

As described above, according to the present invention, since the center of the input or output cavity is offset with respect to the central axis of the drift tube, the electric field distribution inside the cavity is affected by the waveguide. It is uniform even including. Therefore, the electron beam incident on the output cavity interacts with the decelerating electric field of the same magnitude, the generation of retrograde electrons is suppressed, and the beam efficiency and the overall efficiency can be expected to be improved.

Further, in the case of a high power klystron, the electric field inside the cavity becomes uniform, the discharge inside the cavity and the multipactor phenomenon can be suppressed, and stable operation of the microwave tube can be expected.

[Brief description of drawings]

FIG. 1 shows a klystron output cavity according to one embodiment of the present invention.

FIG. 2 is a diagram showing the center of a cavity and the center of a drift tube in the embodiment of FIG.

FIG. 3 is a diagram showing an axial electric field distribution generated in the cavity in the embodiment of FIG.

4 is a diagram showing an electric field distribution (direction parallel to the waveguide) inside the cavity in the embodiment of FIG.

5 is a diagram showing an electric field distribution inside the cavity (in a direction perpendicular to the waveguide) in the embodiment of FIG.

FIG. 6 is a diagram showing a ratio between an offset amount and an electric field strength.

FIG. 7 is a cross-sectional view of an output cavity portion of a multi-cavity klystron.

FIG. 8 is a through view of an output cavity portion of a multi-cavity klystron.

FIG. 9 is a diagram showing an electric field distribution in an output cavity portion.

FIG. 10 is a diagram showing a magnetic field distribution in an output cavity portion.

FIG. 11 is a diagram showing an electric field distribution in the axial direction generated in the cavity.

FIG. 12 Electric field distribution inside cavity (direction parallel to waveguide)
FIG.

FIG. 13: Electric field distribution inside cavity (direction perpendicular to waveguide)
FIG.

[Explanation of symbols]

 1 output cavity 2 drift tube 3 electric field protruding into the cavity 4 electron 5 magnetic field generated inside the cavity 6 waveguide 7 center of drift tube 8 center of output cavity 9 offset amount

Claims (1)

[Claims] 1. An electron gun unit as an electron beam source, a high-frequency circuit unit composed of a plurality of high-frequency cavities that cause the electron beam and microwaves to interact with each other, and an electron beam that has completed the interaction in the high-frequency circuit unit. In the multi-cavity klystron in which the electron gun section, the high frequency circuit section and the collector section are linearly arranged, the input cavity forming the high frequency section is formed. A multi-cavity klystron, wherein the center axis of the body or the output cavity is offset to the side opposite to the input / output waveguide with respect to the center axis of the drift tube for traveling the electron beam.