Experimental Study On The Characteristics Of Hall Thrusters Plume Based On The Image Method

An in-orbit Hall thruster will form an artificial plume plasma environment around the spacecraft,which may lead to the electrical,magnetic,thermal change of the spacecraft and affect its normal and stable work.Therefore,it has important theoretical significance and application value for assessing the plume effect of an in-orbit Hall thruster to study the plume characteristics by means of the ground test and theoretical analysis.Considering the limitations of the common plume diagnosis method in orbit application,this paper presents a plume image diagnosis method,which is applied to the experimental study on the plume characteristics of Hall thrusters.First of all,the luminescence mechanism and the emission spectrum of the Hall thruster plasma plume are analyzed theoretically.The variation of the spectral radiation intensity of the characteristic lines of the plume plasma with the discharge parameters is obtained by experiments.The results show that the discharge voltage,mass flow rate and coil current are the main influencing factors of the plume spectral intensity.Based on the collisional radiation model,the relationship between the plume spectral radiation intensity and the plasma parameters such as electron temperature and particle density was established.On the basis of this,the influence of various discharge parameters on the distribution of the plume electron temperature along the axial direction is studied.The calculated results of the electron temperature are consistent with the variation of the plume spectral radiation intensity,which verify the rationality and reliability of the model and provide the theoretical basis for the future research.Secondly,based on the principle of plume imaging,the relationship between plume image information and light intensity is deduced.The calculation model of plume characteristic diagnosis based on image method is established by combining the collisional radiation model.According to the analysis of the distribution characteristics of plume spectral radiation,the concept of the plume spectral radiation divergence degree is defined,which is an image diagnosis method for assessing the divergence of plume from an optical point of view.Through the comparative experimental study and the theoretical analysis,the digital filtering effect of the image RGB model is revealed,and the reliability of the plume image diagnosis model is verified.Thirdly,the spatial distribution of plume plasma parameters of a Hall thruster is studied experimentally on the basis of the plume image diagnosis model.The results show that the electron temperature,ion density and atom density of theplume are gradually decreased with the increase of the axial distance,and symmetrically distributed along the radial direction of the thruster.The distribution of the plasma parameters is concentrated in the vicinity of the annular discharge channel exit.These conclusions,whether in numerical magnitude or spatial distribution,are in agreement with the existing literature and theoretical analysis.Then,the influence of the discharge parameters on the plume plasma parameters is studied.At the same time,by analyzing the relationship between the plume characteristics and the performance parameters of the Hall thruster,it is suggested that the change of the plume characteristics can reflect the change of its performance indirectly.On the other hand,the rationality of the calculation results further validates the reliability of the model.In addition,the divergence characteristics of the plume are studied.It is showed that when the discharge voltage increases or the mass flow rate decreases,the divergence divergence decreases.The divergence variation is consistent with the traditional divergence angle,which indicates that plume spectral radiation divergence degree can effectively evaluate the divergence degree of plume.Finally,the adaptability and uncertainty of the plume image diagnosis method are studied.The adaptability of the diagnostic method to with different discharge channels and in different plume areas is analyzed by studying the variation of the plume plasma parameters for the corresponding conditions.Then,the uncertainty of the plume image diagnosis method is studied by the error analysis caused by the image measurement factors,such as camera shooting parameters and shooting position,and the image calculation model,and the corresponding applicable conditions and scope are given.