Study Of Magnetic Shielding Configuration And Plasma Discharge Characteristics In Hall Thruster

Hall thruster is a kind of electrical propulsion device for spacecraft.It has many advantages such as high efficiency,high specific impulse and high reliability.It has been widely used in spacecraft atmospheric drag compensation,position maintenance,attitude adjustment,orbit correction and other tasks.With the continuous development of space technology such as space station and deep space exploration,the demand for the service life of Hall thruster is increasing greatly.The main factor restricting the lifetime of Hall thruster is the sputtering corrosion of ions on the wall in the discharge channel.Magnetic shielding technology uses electromagnetic coils to construct magnetic shielding field configuration,which can restrain plasma,reduce the interaction between ions and the wall.It is of great significance to reduce wall corrosion of thruster duct and prolong on-orbit life.In this thesis,based on the channel structure of Hall thruster and plasma discharge process,a two-dimensional axisymmetric physical model is established.The optimized magnetic shielding field is constructed by FEMM software.The plasma discharge process of Hall thruster under magnetic shielding field is studied by particle-in-cell simulation method.By adjusting the structure of the magnetic circuit,changing the position of the magnetic screen and moving the magnetic pole outward towards the outlet of the channel,the magnetic shielding field configuration of the discharge channel of the thruster was designed to make better ion beam focusing.The effects of magnetic shielding field intensity on plasma density,axial electric field,electron temperature,potential,ion radial velocity distribution and collision frequency between particles and wall of Hall thruster discharging process are studied.The results show that with the increase of the intensity of the near-wall axial magnetic field,the focusing of ion beam increases,the near-wall potential increases,and the collision frequency between particles and the wall decreases significantly.The electron temperature in the channel is relatively high,the electron temperature near the wall and the anode is low,which is conducive to the ionization of propellant;the radial velocity of the near-wall ion decreases continuously,and the energy decreases when the ion collides with the wall,which is conducive to reduce wall corrosion and prolong the lifetime of thruster in orbit.The effect of magnetic shielding configuration on plasma discharge parameters in Hall thruster channel is studied.By optimizing the configuration of magnetic shielding field,the electron temperature rises in the central region of the channel,the electron temperature near the wall and the anode is lower,and the ionization rate increases;the channel near the wall potential is higher than the channel center potential,which restrains the radial movement of ions and improves the plume focusing;the collision frequency between ions and the wall decreases by 10.8%,and the average radial velocity of ions on the inner wall decreases by 22.6%,and the specific impulse also increases,which improves the performance of the thruster.