Research On Ku Band Overmoded Relativistic Klystron Amplifier

The power capacity of a single high power microwave sources is limited by the physical conditions,and space power synthesis technology can make a set of high power microwave?HPM?devices output synergistically,for obtaining the greater microwave power radiation output.Relativistic klystron?RKA?has the characteristics of high efficiency,high power,high gain,stable output phase and frequency.It is the focus of the research on space power synthesis technology.This paper presents a novel Ku band high gain overmoded structure of relativistic klystron,the design of radial RKA with hollow structure is simple,with the working mode of TM₀₂ mode in cavities,and high power capacity of device is achieved in the Ku band.In order to solve the problem of multi-mode superposition interference caused by the overmoded structure,relevant research has been carried out.The research contents of this paper include the following aspects.Firstly,the characteristics of overmoded klystron are studied theoretically.By using the classical method of analyzing the klystron,the analysis of overmoded klystron is made in several aspects like space limit current,beam coupling coefficient and electron beam loading conductance.And a preliminary understanding of the characteristics of overmoded klystron is obtained.Secondly,the working cavities are designed for the radial mode structure.In order to simplify the structure,the device adopts a hollow circular waveguide structure,with the drift section radius of approximately 3/4?.Using the reentrant cavity into the structure for injecting microwave,the input cavity realizes the matching rate of 95%of injected microwave.In order to improve the modulation depth and the overall gain of klystron,two-stage group of bunchers are adopted.Design of double gap output cavity is made in a hollow circular waveguide on the basis of keeping extraction structure simple.The particle simulation software is used for the analysis the characteristics of each structure.In order to increase the independence between the cavities in the case that the drift section does not cut off the TM₀₁ mode,two sections of absorbing material are adopted to absorb the microwave to suppress the self excitation interference caused by the microwave leakage.Finally,the 2.5 dimensional particle simulation software is used to simulate the Ku band overmoded klystron amplifier,and the beam-wave action process and microwave generation mechanism are studied and analyzed carefully.In the case of guiding magnetic field 1.0 T,a microwave with a average power of¹ GW is generated by an IREB with a voltage 580kV and a current of 7.3 kA.The frequency and power of the input microwave is 14.25 GHz and 50 kW.The extraction efficiency is 23.6%and the gain is about 43dB.The output mode is mainly TM₀₁ mode.After the output cavity is optimized after chamfering,the maximum field strength drops to 1.45MV/cm when the output power is basically unchanged.The influence of diode voltage and injection microwave on the working state of the device and the phase lock of the output microwave are also studied.