Design And Simulation Of Hall Ion Source

In recent years,with sophisticated industrial products for the material processing requirements are increasing,especially the coating and etching process,the traditional electron beam thermal evaporation technology and chemical etching technology is more and more difficult to meet the demand of industry,so people began to focus on the plasma technology for aerospace propulsion.In view of the above situation,this paper proposes a kind of cylindrical Hall ion source with new structure.This hall ion source is energized by a single internal permanent magnet ring,which forms the cylindrical discharge channel.The new ion source has large range of plasma density distribution and uniform distribution of plasma energy.For this new cylindrical Hall ion source,a series of studies have been carried out,including the magnetic field near the anode,the magnetic field at the outlet of the channel,gas homogenization and the erosion at the bottom of the discharge channel.Firstly,the discharge and plume parameters of this cylindrical Hall ion source are diagnosed.And two important design criteria of Hall ion source are summarized,including the spatial distribution of plasma density and plasma energy.The influence of the magnetic field near the anode on the thermal deposition of the ion source anode is studied in order to solve the problem that anode is overheating under high voltage working condition.The results show that the weakening of the magnetic field near the anode can significantly reduce the electron temperature reaching the anode surface.So an optimization scheme of anode magnetically insulation is proposed to weaken the magnetic field near the anode in this paper in order to improve the deterioration of anode thermal deposition under high voltage condition.In addition,the influence mechanism of the near anode magnetic field and ion source beam angle is analyzed.The results show that the change of the magnetic field near the anode brought by the preposition of the anode could further improve the spatial distribution of plasma density.Secondly,the influence of magnetic field at the outlet of the discharge channel of the cylindrical Hall ion source on discharge and plume characteristics is studied and analyzed.Two methods are proposed to change the magnetic field at the outlet of the channel,including changing the length of the external magnetic pole and the length of the ceramic channel.The results show although the change of pole length can slightly improve the ionization of ion source,it has no obvious effect on the plume divergence and brings deterioration to ion energy distribution.However,the shorten of ceramic channel increases the magnetic field strength gradually and makes magnetic field lines at the outlet bending in the opposite direction to the channel axis.The results show that the change of ceramic channel makes the plume divergence angle larger,which means better spatial distribution of plasma density,and more uniform of spatial distribution of ion energy.Thirdly,aiming at the gas homogenization in the discharge channel of cylindrical Hall ion source,the influence of two circumferential outlet modes on discharge and plume characteristics is studied.The COMSOL simulation results show that the neutral gas density distribution of the inner circumferential outlet mode is better than the outer circumferential outlet mode in the discharge channel length of 0.1 to 1.The PIC results show that the ionization of inner circumferential outlet mode is indeed better,but the outer circumferential outlet mode has a larger divergence angle.However,the overall spatial distribution of ion energy does not change significantly.Finally,aiming at the erosion phenomenon found in the long-time work process of the cylindrical Hall ion source,this paper analyzes the mechanism of this kind of erosion.The results show that the erosion phenomenon at the bottom of discharge channel is caused by the ions back bombardment.This paper also proposes to use the magnetic mirror effect in the discharge channel to slow the erosion phenomenon.The PIC results show that with the magnetic mirror ratio increasing,the ion flux and ion energy reaching the bottom of the discharge channel is decreasing.So the deposition power density at the bottom of discharge channel is reduced greatly,and the erosion phenomenon is indeed slowed.