| When designing electron devices,it is often necessary to analyze some particle phenomena,such as the interaction between particles and electromagnetic fields,secondary electron emission,and collisions between particles.Deeply studying the particle behavior in electron devices is of great significance for optimizing the design of electron devices and improving their performance.Due to the ability to accurately describe the physical characteristics of the particle phenomenon from transient to steadystate and from microscopic to macroscopic,the PIC(particle-in-cell)method plays an important role in the simulation and study of particle characteristics of electron devices.Then various high-performance commercial PIC software has been developed.With the rapid development of computers,the application of PIC software has become increasingly widespread.However,there is still a certain gap in maturity and computational efficiency between domestic PIC software and foreign PIC software.Therefore,researching and developing high-efficiency PIC software with independent intellectual property rights and breaking the monopoly of foreign software is of great significance for the future development of related fields in China.To solve the problem of the low maturity and computational efficiency of existing PIC software in China,this study focuses on high-efficiency PIC software and mainly includes the following four parts.In the first part,high-efficiency algorithms used in PIC software are studied.The conformal finite-difference time-domain(CFDTD)algorithm is extended to non-uniform grids to update the electromagnetic field.The movement half interpolation(MHI)method is proposed to improve the calculation efficiency of the particle motion.A scheme combining the continuity equation of the current source with the zigzag algorithm is proposed to solve the distribution of the current source.This algorithm solves the problem of the charge conservation under non-uniform grids.The PIC algorithm is paralleled based on GPU,which improved the solving efficiency obviously.At last,we improve Vaughan and Furman secondary electron emission algorithm and introduced the Russian roulette particle merging method to the simulation process of secondary electrons.The particle merging method reduces the number of particles and increases the calculation efficiency of secondary electron problems.In the second part,a high-efficiency PIC software BUMBLEBEE is developed.BUMBLEBEE has a high maturity with various pre-and post-processing functions and excellent stability.This section presented the software framework,pre-and postprocessing modules,and solver modules of BUMBLEBEE.Then an impedance transformer,an extended interaction klystron,and a folded waveguide traveling wave tube are simulated.By comparing the calculation results with CST version 2022,the correctness and efficiency of BUMBLEBEE are verified.In the third part,BUMBLEBEE is used to study the multipactor.Firstly,the research background,significance,and domestic and foreign research trends of multipactor are introduced.Then,the multipactor of an impedance transformer and a ridge waveguide filter is simulated by BUMBLEBEE.The simulation multipactor thresholds of these devices are achieved,they are in good agreement with experimental results by over 88%.This verifies the effectiveness and reliability of BUMBLEBEE in studying multipactor.For the impedance transformer,the relationship between harmonics and secondary electron spatial distribution has also been established.This result has important theoretical guidance for determining the occurrence area of multipactor in devices and then optimizing the design of the device to increase its stability. |
