Research On High Efficiency Microwave Extract Technology Of S-band Relativistic Klystron

Relativistic Klystron Amplifier(RKA)is a microwave device with an output power of GW magnitude,which electron beam generation,beam-wave interaction and electron beam collection are done separately in different regions.Therefore,it has many advantages,such as high power,high gain,high efficiency and high stability.RKA is the device with the highest pulse power and average power in microwave electric vacuum devices.At present,microwave output efficiency of RKA is low.In order to obtain a higher power,the cathode must be given a large enough emit voltage and current,which requires a high performance accelerator.Therefore,it is important to improve the output efficiency of RKA.The extract efficiency of the output cavity has an important influence on the efficiency of the whole RKA.In this paper,the output cavity theory of S-band RKA is investigated.The high-frequency characteristics and particle simulation of double-gap output cavity and single-gap output cavity are calculated.Finally,the secondary extract cavity is designed and simulated by PIC particle simulation software.The main work of this paper include the following aspects:Based on the large-signal theory of one-dimension disk model,the law of output cavity equivalent circuit model is analyzed,the electronic efficiency relation of singlegap output cavity and double-gap output cavity are deduced.Finally,the relation between electronic efficiency and multiple variables are obtained.Based on the theories of relativistic effect,space charge effect and design ideas of conventional high power klystron amplifier,the electron beam parameters,focusing parameters,beam interaction parameters and resonate parameters of the output cavity are determined.The resonant frequency and field distribution of the closed cavity of the double gap output cavity and the single gap output cavity are obtained.The double-gap output cavity and single-gap output cavity model are designed.Some high frequency characteristic which including the resonant frequency,field distribution,loaded Q value and characteristic impedance are calculated.The double-gap output cavity is simulated through the 2.5-dimension electromagnetic particle simulation software.The microwave extraction and the residual energy distribution of the electron beam are observed.Then,according to the residual energy distributing of the electron beam,the voltage value of the single-gap output cavity is determined and the single-gap output cavity is simulated based on this value.Finally,the secondary extract cavity is designed,simulated and optimized.The particle simulate result show that the total radiation microwave power 3.5GW can be generated in the condition of electron beam voltage 900 keV,current 7.5kA,fundamental current modulation depth 100% and axial guidance magnetic field 1.2T.The primary extract cavity can output power 2.5GW and the secondary extract cavity can output power 1.0GW.The total efficiency is about 52%.Finally,the relationship between multiple parameters and efficiency is analyzed.