Study On Beam Distribution Characteristics Of Magnetically Shielded Hall Thruster

With the development of space electric propulsion technology and the proposal of all electric propulsion satellite platform,electric propulsion technology has attracted unprecedented attention.Magnetically shielded Hall thruster is the optimized product of Hall thruster.Its unique magnetic field configuration and wall matching design reduce the wall erosion rate by at least 2-3 orders of magnitude.On the premise of ensuring high specific impulse,high thrust and high reliability,this technology greatly increases the life of the thruster,greatly widens the application of Hall thruster,and has a broad application prospect.However,since there is no wall constraint in the acceleration region and the large radial electric force,the divergence of the magnetically shielded Hall thruster plume is more serious,which restricts its development and application.Based on this,the simulation and experiment of the influence factors of the plume of the magnetically shielded Hall thruster are carried out in this paperFirstly,the influence of the tilt direction of the magnetic field lines on the beam characteristics in the magnetic shield Hall thruster is studied.By adjusting the pole,different tilted shapes of the magnetic lines are designed,which are inclined in,flat and tilted out.Based on the experimental data,the simulation analysis is carried out and compared the results with the traditional Hall thruster.The simulation results show that the ion density in the channel center of the magnetically shielded Hall thruster is higher,the plume divergence is smaller,and the discharge performance is better when the magnetic field line is in the form of inclination.Secondly,the influence of the shape of magnetic seperatrix on the beam characteristics in magnetically shielded Hall thruster is studied.By adding a local shell to change the shape of the magnetic seperatrix,the different shapes of the magnetic seperatrix and whether the magnetic seperatrix is included or not are simulated.The simulation results show that the closer the cathode boundary is to the magnetic seperatrix,the earlier the electron heating process occurs,the smaller the radial electric field is,and the better the thruster performance and the better the plume focusing are presented.In addition,the difference between the simulation and the reality are analyzed,and the effect of electron path on electron temperature should be considered in practice.Thirdly,the influence of cathode position on the beam characteristics in the magnetically shielded Hall thruster is studied.Moving cathode positions with fixed angle in 2D experiment,moving cathode in three degrees of freedom experiment in iron core magnet thruster and moving cathode in three degrees of freedom experiment in circumferential annual coil thruster were designed to determine the optimal cathode working position and angle.When the cathode is in the optimal working position,the recombination of electrons and ions takes place earlier,and the number of ions in the plume decreases rapidly with distance,which reduces the radial electric field force in the plume,and the plume has a better focusing property.Finally,the effects of different pole materials and pole potentials on the beam characteristics in magnetically shielded Hall thruster are studied.The simulation results show that when the magnetic pole material is ceramic,the secondary electrons emitted by the ceramic enter the channel,increasing the density of electrons and ions in the channel,so the current and thrust of the thruster are larger,and the radial electric field of the ceramic pole is smaller,and the plume divergence is smaller;when the potential of the magnetic pole is high,the axial and radial electric field gradients out of the channel decrease,but the radial electric field gradients decrease even greater,with little divergence of the beam.