CN209312710U - A Hot Cathode Microwave Electron Gun for Suppressing High-Order Mode Electromagnetic Fields - Google Patents

Abstract

The utility model relates to a kind of THERMIONIC CATHODE MICROWAVE ELECTRON GUNs for inhibiting high-order mode electromagnetic field, including half chamber, whole chamber and coupling edge chamber to link together；Half chamber is equipped with cathode, and top is equipped with half chamber coupling aperture, and bottom is equipped with half chamber corresponding with the half chamber coupling aperture and couples symmetrical holes；The waveguide aperture for being respectively equipped with coupling aperture on the whole chamber, being connected with waveguide, the whole chamber corresponding with the waveguide aperture are equipped with guide symmetry hole；The middle part of the whole chamber and half chamber is equipped with electron beam channel, and the end of the electron beam channel is equipped with electron beam outlet；The top of half chamber and the whole chamber is connected by the half chamber coupling aperture, the coupling aperture with the coupling edge chamber respectively, it is characterised in that: the whole bottom of chamber portion is equipped with whole chamber corresponding with the coupling aperture and couples symmetrical holes.The utility model reduces second order mode and influence of the quadravalence mould to quality of beam, improves electron beam quality of beam by way of aperture symmetrical in resonant cavity.

Description

A Hot Cathode Microwave Electron Gun for Suppressing High-Order Mode Electromagnetic Fields

technical field

The utility model relates to the technical field of hot cathode microwave electron guns, in particular to a hot cathode microwave electron gun for suppressing high-order mode electromagnetic fields.

Background technique

Hot cathode microwave electron gun is an electron beam generating device with large charge and short pulse. It has been valued by most countries and has produced considerable scientific research value and social benefits in major scientific research countries. It is widely used in high-energy electron accelerators Construction, medium and low energy electron beam beam generation and other scientific research. The hot cathode microwave electron gun used for electron beam generation in foreign countries mainly adopts the classic structure of APS type, because this structure has many advantages such as high beam intensity, high charge amount, long cathode life, easy maintenance, and good safety. Types of experimental high-energy electron accelerators have adopted APS-type hot cathode microwave electron guns as one of the main equipment for electron source generation.

Although the APS type hot cathode microwave electron gun uses the hot cathode to generate electron bunches and extract the electron beams through the microwave field, it has certain advantages in the charge amount and pulse width of the electron beam macropulse, but due to the coupling of its structure and the microwave electric field, The electromagnetic fields of the second-order mode and the fourth-order mode have a great influence on the beam quality.

Utility model content

The technical problem to be solved by the utility model is to provide a hot cathode microwave electron gun which can improve the beam quality of the electron beam and suppress the high-order mode electromagnetic field.

In order to solve the above problems, the hot cathode microwave electron gun for suppressing the high-order mode electromagnetic field described in the utility model includes a half cavity, a whole cavity and a coupled side cavity connected together; the half cavity is provided with a cathode, and the top thereof is provided with a A half-cavity coupling hole, the bottom of which is provided with a half-cavity coupling symmetrical hole corresponding to the half-cavity coupling hole; the upper part of the whole cavity is respectively provided with a coupling hole and a waveguide hole connected with a waveguide, corresponding to the waveguide hole The whole cavity is provided with a waveguide symmetrical hole; the middle of the whole cavity and the half cavity is provided with an electron beam channel, and the end of the electron beam channel is provided with an electron beam outlet; the half cavity and the whole cavity are provided with an electron beam outlet; The top of the cavity is respectively connected with the coupling side cavity through the half cavity coupling hole and the coupling hole.

Compared with the prior art, the utility model has the following advantages:

The utility model designs a new type of hot cathode microwave electron gun on the basis of the design scheme of the existing APS type hot cathode microwave electron gun by adopting the improved method of opening holes at the symmetrical positions of the coupling holes in the cavity. , reducing the influence of the second-order mode and the fourth-order mode on the beam quality, and improving the beam quality of the electron beam, which is a major improvement to the classic APS type microwave electron gun.

Description of drawings

The specific embodiments of the present utility model will be described in further detail below with reference to the accompanying drawings.

Figure 1 is a schematic structural diagram of the utility model.

Figure 2 is a cross-sectional view of the utility model.

Figure 3 is a side view of the utility model.

Fig. 4 is the microwave characteristic of the electron gun of the utility model.

FIG. 5 is the electric field corresponding to the π/2 mode of the present invention.

FIG. 6 is the magnetic field corresponding to the π/2 mode of the present invention.

Fig. 7 is the electric field distribution on the axis of the utility model.

Fig. 8 is the multi-level field component strength test position of the utility model.

Fig. 9 is the normalization of each position of the utility model weight.

FIG. 10 is the phase space distribution of the beam current characteristics at the exit of the electron gun of the present invention (A) energy distribution (B, C, D).

In the figure: 1-half cavity; 2-whole cavity; 3-coupling side cavity; 4-half cavity coupling hole; 5-half cavity coupling symmetrical hole; 6-coupling hole; 7-waveguide; 8-waveguide symmetrical hole; 9 - electron beam exit; 10 - coupling symmetrical hole in the whole cavity.

Detailed ways

As shown in Figures 1-3, a hot cathode microwave electron gun for suppressing high-order mode electromagnetic fields includes a half cavity 1, a whole cavity 2 and a coupled side cavity 3 that are connected together. The half-cavity 1 is provided with a cathode, its top is provided with a half-cavity coupling hole 4, and its bottom is provided with a half-cavity coupling symmetrical hole 5 corresponding to the half-cavity coupling hole 4; the whole cavity 2 is provided with a coupling hole 6, The waveguide hole of the waveguide 7 is connected, and the whole cavity 2 corresponding to the waveguide hole is provided with a waveguide symmetrical hole 8; the middle of the whole cavity 2 and the half cavity 1 is provided with an electron beam channel, and the end of the electron beam channel is provided with electron beam channels. Beam outlet 9; the tops of the half cavity 1 and the whole cavity 2 are respectively connected with the coupling side cavity 3 through the half cavity coupling hole 4 and the coupling hole 6; the bottom of the whole cavity 2 is provided with a whole cavity coupling symmetrical hole 10 corresponding to the coupling hole 6 .

Since the state of the electron gun during actual operation is different from that during processing and assembly, it is necessary to consider the adjustment of the design target (mainly frequency) when designing the electron gun, as shown in Table 1. The target frequency of the electron gun was set at 2855.6 MHz during design and processing.

Table 1 Frequency values of electron gun in different states

Since the hot cathode electron gun adopts an edge-coupling structure, it is necessary to establish a three-dimensional model for microwave design. The size parameters are shown in Figure 4.

The simulation design is carried out by the F module, and the main simulation results are shown in Table 2 and Figure 4.

Table 2 3D design results of electron gun

The electric and magnetic field distributions corresponding to the π/2 mode are shown in Fig. 5 and Fig. 6. It can be found that the phase difference of the electromagnetic field in the half cavity and the whole cavity is π, while there is no electromagnetic field in the side cavity. The electric field distribution on the axis (see Fig. 7) is adjusted to enhance the half-cavity with a maximum field strength ratio of 1.64, which is designed according to the dynamic optimization requirements.

In order to better optimize the emissivity of the electron gun outlet, the multi-level field is suppressed by adding and adjusting coupling holes in the design of the electron gun. As shown in Figure 8, due to the opening of waveguide holes and coupling holes in the whole cavity, there is angular asymmetry in the whole cavity, and a second-order component is introduced, resulting in the overall lateral momentum of the electron gun exit beam. In order to suppress this second-order component Due to the effect of the field component, the whole cavity coupling symmetrical hole is introduced into the electron gun, and the symmetrical hole on the opposite side of the waveguide and the size of the symmetrical hole in the half cavity are adjusted (strictly according to the length and width of the whole cavity waveguide hole, it is opened at the symmetrical place in the whole cavity. hole).

Three circles with a radius of 10mm at different axial positions in the electron gun are selected, as shown in Figure 8, two of which are near the nose cone of the half cavity and the whole cavity, and the other is in the center of the whole cavity. on these three circles The components are optimized for the standard electron gun design to make the secondary field components smaller, as shown in Figure 9 and Table 3. It can be found that except the fourth-order field in the half cavity is slightly taller, the second-order field in the whole cavity is reduced by an order of magnitude, which can greatly reduce the lateral momentum introduced by the second-order field.

Table 3 Multilevel field components at each location

The motion of electrons was studied by simulating a longitudinally uniform electron beam cluster with a time of 350ps for one RF period using OPAL-T. The microwave field files used are obtained from CST simulations, and space charge effects are considered in the simulations. The main parameters are shown in Table 4.

Table 4

Figure 10 reflects the energy distribution at the electron beam exit (under different field strengths), the spatial distribution in the XY directions, and the respective phase space distributions in the X and Y directions.

Claims (1)

1. A hot cathode microwave electron gun for suppressing a high-order mode electromagnetic field, comprising a half cavity (1), a whole cavity (2) and a coupled side cavity (3) connected together; the half cavity (1) is provided with a cathode, which is The top is provided with a half-cavity coupling hole (4), and the bottom is provided with a half-cavity coupling symmetrical hole (5) corresponding to the half-cavity coupling hole (4); the upper part of the whole cavity (2) is respectively provided with a coupling A hole (6), a waveguide hole connected with a waveguide (7), a waveguide symmetrical hole (8) is arranged on the whole cavity (2) corresponding to the waveguide hole; the whole cavity (2) and the half An electron beam channel is arranged in the middle of the cavity (1), and an electron beam outlet (9) is arranged at the end of the electron beam channel; the tops of the half-cavity (1) and the whole cavity (2) respectively pass through the half-cavity The coupling hole (4) and the coupling hole (6) are connected to the coupling side cavity (3), and it is characterized in that: the bottom of the whole cavity (2) is provided with an integral part corresponding to the coupling hole (6). Cavity coupling symmetrical hole (10).