Particle-in-Cell Numerical Simulation Study On The Matching Characteristics Between Magnetic Topology And Channel Morphology In Magnetically Shielded Hall Thruster

With the application of comprehensive electric propulsion technology,it provides opportunities and challenges for Hall thruster.The development trend of space missions is longer execution cycle,more targets and longer distance,which puts forward tens of thousands of hours of life-span requirements for thrusters.Magnetically shielded technology can effectively reduce the effect of ions bombardment on the wall,wall erosion is no longer the decisive factor restricting the service life.This technology is an essential key technology in the application of Hall thruster in the future.On the one hand,the magnetically shielded technology is to form an inward concave and outward shift magnetic field,on the other hand,it is necessary to ensure that the wall and the magnetic field line match.Based on these two problems,this paper simulated and analyzed the matching process of magnetic topology and wall morphology in magnetically shielded Hall thruster.The first is to optimize the Full-PIC program.According to the motion characteristics of electrons in the channel,the channel is divided into different regions.Determine the conductivity and electron conduction process in different regions.In the traditional Hall thruster,the inner and outer Bohm coefficients are divided by the channel area,while in the magnetically shielded thruster,the Bohm coefficients are divided by the magnetic field gradient,so as to realize the suppression process of the positive gradient magnetic field to the electron.The selection of Bohm coefficient is modified by experimental data to ensure that the simulation results are true and reliable.Secondly,the influence of different outward shifts of magnetic field on the discharge characteristics under the matching mode of magnetic field line and wall is studied.By changing the relative position and angle of magnetic poles,the magnetic field structure with the same maximum magnetic field intensity but different outward shifts is obtained.It is found by numerical simulation that with the outward shift of the magnetic field,the positions of the ionization and acceleration region also move downstream,which significantly affects the atomic density and the interaction between high energy ions and the wall.When the wall is matched with a specific magnetic field line,it can achieve a better magnetic shielding effect.Through the performance characteristics and magnetic shielding effect,the best outward shift magnetic field is selected,and the suitable installation position of cathode is selected.Then,the wall topography matching with different magnetic field lines is designed,and the similarities and differences of discharge characteristics under different matching are analyzed by PIC simulation,and the best matching magnetic field lines are selected.The selection of the magnetic field line has a significant effect on the chamfer flow aera,which decides the density distribution of the atoms in the channel,and the characteristics of ionization and acceleration.When the matching position is closer to the exit section,it has better performance and more serious wall erosion,so the appropriate wall morphology should be selected.Finally,the problems existing in the actual processing and engineering application are considered.The application of magnetic shielding field can ensure the long life of thruster.Using the straight channel wall shape,the processing is simple and the accuracy is low.The smaller the chamfered shape,the longer the channel,the better the discharge characteristics of the thruster.For task requirements,it has higher total specific impulse and stronger task completion ability.In addition,the over matching morphology can also meet the magnetic shielding requirement.Through the study of the discharge characteristics under the over matching morphology,the application value of the over matching morphology in engineering application is analyzed.