Research On Electromagnetic Characteristics Of Discharge Chamber Of Ion Thruster

Due to the high efficiency,high specific impulse,long lifetime,and small volume,ion thrusters are widely used in earth-orbiting satellites,deep space exploration,and interstellar navigation tasks.The discharge chamber is the main component of the ion thruster to produce plasma,and its discharge efficiency directly affects the performance of the thruster.However,due to the limitations of experimental cost and numerical computing power,many discharge mechanisms inside the chamber are still not well understood,which limits its further optimization and improvement.Therefore,this dissertation develops a high-performance computational model of the discharge chamber to study the key physical issues such as the plasma characteristics,external magnetic field configurations,and the dynamic electromagnetic effect,aiming to further understand the discharge behavior of the chamber and the essential factors affecting its discharge efficiency.The research content is mainly divided into five parts:1.Research on particle model of the discharge chamber.Based on the PIC/MCC method,a 2D fully kinetic particle model was developed to study important aspects of the discharge chamber.The model tracks four kinds of particles in detail,and considers five kinds of collision processes between particles;the model accurately calculates the interaction between charged particles and electromagnetic field,and carefully deals with the boundary conditions of various particles;the model improves the solution methods of the PIC/MCC core sub-modules,such as using the multigrid method to solve the electric potential,using the Zigzag method to calculate the current density and so on;the model has been verified by commercial software and has high calculation accuracy and efficiency,which lays a foundation for the research of discharge chamber.2.Research on optimization of the simulation algorithm.In response to the challenges in the fully kinetic simulation of the discharge chamber,a variety of optimization techniques have been developed.For example,the self-similarity method and the multistage increase of permittivity method are used to simplify the model to speed up the calculation;the implicit PIC method is used to deal with the stability constraints of PIC/MCC simulation;the sub-cycle time technique is used to solve the large difference in particle motion scale;the Open MP parallel scheme based on domain decomposition is used to solve the computational inefficiency;the particle merging algorithm based on the Voronoi diagram is used to handle the limitation of too many particles.The advantages and disadvantages of these technologies are evaluated in detail and combined with the traditional PIC/MCC algorithm to create conditions for breaking through the limitations of the full dynamic simulation of the discharge chamber.3.Research on the characteristics of plasma discharge.The plasma discharge process under complex physical conditions was simulated,and a series of steady-state discharge results including plasma density,energy,potential,and discharge loss are obtained.The simulation results are consistent with the experimental results,which verify the effectiveness of the calculation model.The effects of plasma distribution,magnetic confinement,dynamic electric field,neutral gas loss,and gas flow rate on discharge efficiency are elaborated from a microscopic perspective,which improves the understanding of the discharge mechanism of the discharge chamber.4.Research on the influence of the external magnetic field.Different magnetic field structures were designed,and the influence of closed magnetic field strength,magnetic field topography,and the number of magnetic rings on the discharge parameters were studied.The results show that increasing the closed magnetic field strength can improve the plasma confinement and ionization efficiency,and increasing the number of magnetic rings can improve the magnetic field lines and plasma density uniformity.By combining the advantages of both,the discharge efficiency and grid erosion can be improved at the same time.The simulation reveals the dependence of plasma confinement and loss,discharge efficiency,and beam uniformity on the magnetic field configuration,which provides insights for optimizing the magnetic field structure design.5.Research on dynamic electromagnetic characteristics.The simulation difference between electrostatic model and electromagnetic model of the discharge chamber was compared,and the effect of the dynamic electromagnetic field was discussed.The multistage increase of permittivity method and the full electromagnetic model work together to study the interaction between plasma and electromagnetic field.This effort aims to supplement the lack of electromagnetic study on the discharge chamber and provides references for the studies of electromagnetic radiation effects and electromagnetic compatibility.