Research On Key Technologies Of S-Band Multi-Beam Klystron

The klystron is a microwave electronic device that oscillates or amplifies based on the periodic modulation of the electron beam velocity.Compared with the single beam klystron,the multi beam klystron has more electron beam number in structure,while the multi beam klystron has higher output power and gain and higher electron conversion efficiency in performance,at the same time,it can realize the energy conversion in a wider frequency band under the condition of low voltage.The multi-beam klystron has attracted more attention because of its unique superiority.It has been successfully used in radar navigation,radiation detection,linear collider and other fields.In this paper,we conduct theoretical research and particle simulation research on multi-beam klystron high-frequency interaction system and input-output system,aiming to realize a S-band broadband 100 k W microwave energy output multi-beam klystron.The theoretical research on the high frequency interaction system of the klystron mainly focuses on the analysis of the speed modulation and clustering of the electron beam,the space charge wave theory,the one-dimensional electron disk model,the two-dimensional electron ring model and the self-excited oscillation mechanism of the klystron.Then,according to space charge wave theory and klystron large signal theory,the initial structural parameters of the S-band high-power multi-beam klystron were calculated,and the working parameters of the corresponding multi-beam klystron were optimized through simulation design.The structure parameter design mainly includes the size of each cavity,the length of drift tube,the area and thickness of loss,the size of input and output system,etc.Meanwhile,in order to make the multi beam klystron work stably in a wider frequency band and at a higher output power,the input and output systems are designed with coaxial and waveguide filter loading structure respectively.The design of working parameters mainly includes accelerating voltage,electron beam current and working magnetic field under the condition of obtaining stable single-mode output.The research of the output window of the multi-beam klystron is conducted from the aspects of the output window material,structure and processing technology.In this paper,the microwave output window adopts the dumbbell structure,which can not only meet the design requirements,but also play a role in suppressing the "ghost mode" oscillation.Finally,the standing wave ratio is less than 1.12 in the 2.75ghz-3.05 ghz broadband frequency range,ensuring the stable transmission of microwave energy under the rated power.Finally,using the initial structure parameters and initial working parameters of the multibeam klystron,combined with the results of the research on the mechanism of the multibeam klystron,the whole modeling and optimal simulation design of the S-band high-power multibeam klystron are carried out to achieve the S-band broadband 100 kilowatt level microwave energy output.The simulation results show that when the accelerating voltage of the multi beam klystron is 24 k V,the total electron beam current is 21.4a,and the input signal power is 28.13 w,the electron beam can interact with the high frequency field through the input cavity,four intermediate cavities and the output cavity.The maximum output microwave signal power of the multi beam klystron is 149 kw,the conversion efficiency is more than 29%,the power gain is more than 37 db,and the bandwidth of output power is more than 100 MHz,which meets the design requirements of klystron and verifies the feasibility of the design idea.