Research On Secondary Electron Energy Spectrum And The Relationship With The Threshold Of Multipactor

Multipactor discharge,known as the resonant secondary electron avalanche effect,is a phenomenon caused by secondary electron emission（SEE）and its synchronism with electromagnetic wave.With the development of space industry,high-power payloads are used more and more widely,and multipactor become much more serious problem.When it occurs,accelerated electrons deposit considerable energy on a tiny spot,leading to power dissipation,electrical performance degradation,surface damage,and even irreversible device destruction.Therefore,protecting artificial satellite stable in space is a much more serious problem for space industry.This thesis aims to get an improved energy spectrum model,and explores the relationship between energy spectrum and multipactor threshold.This thesis summarized the existing models of energy spectrum.Furman gave the model that incorporated reflection,making the distinction between different probabilities for secondary emission,inelastic and elastic scattering.However,there were many unphysical parameters in Furman model,which made the exact fit very difficult.Chung and Everhart presented a simple highly idealized calculation of the energy distribution of low-energy secondary electrons.However,this model only described the true-secondary electron of SEE.An improved numerical model was proposed to simplify the fitting process and improve the efficiency of simulation based on the analyzing of Furman model and C-E model.In order to explore the relationship between energy spectrum and multipactor threshold,we used the EM-PIC method with the Furman model and improved model to predict the multipactor threshold with different SES distribution,where the SEY keeps the same.Simulation results indicate that multipactor threshold increases when the proportion of electrons in the low energy end of energy spectrum increases.In order to testify the accuracy of the improved model,we fabricated some pieces of transformer with different metal-coated.We measured the secondary electron emission properties of the samples,and fitted the measurement data with theimproved model.Then,we simulated the multipactor with the fitted model and compare with the multipactor results of experiment.Simulation and experiment results demonstrate that the threshold prediction accuracy of 0.3d B in the multipactor simulation is reached.This thesis explored the relationship between the accumulation of multipacting electrons and the variation of the transmission properties in microwave components.An equivalent media model is proposed to describe the electron accumulation during multipactor,where effects of the electrons’ accumulation were approximated as a media with special relative permittivity.Simulation and calculation results indicate that the transmission properties of the microwave components remain unchanged when the density of electrons increased from 0/m³ to 1×10¹⁶/m³ during multipactor.However,the return loss in the pass band frequencies dropped 15 d B when the electron density met 1×10¹⁷/m³.The transmission was even cut off when the density of electrons increased to the magnitude of 4×10¹⁷/m³.The effect of electronic collision frequency has also been considered in this thesis.Simulation and calculation results indicate that the electronic collision frequency has a big impact on transmission properties if the electron density is 1×10¹⁷/m³ and electronic collision frequency up to 1×10⁹Hz.What’s more,electronic collision frequency becomes the main influential factors at the frequency met 1×10¹¹Hz.