Numerical Investigation On Helicon Discharges And Electromagnetic Acceleration For Inductive Plasma Thruster

Electromagnetic thruster has the advantages of high ionization efficiency,wide propellant choice and high specific impulse,and is the ideal choice of space propulsion.This thesis gives special emphasis on the helicon plasma discharges and acceleration,with the background of micro-satellites propulsion.The uniform and non-uniform helicon discharge and the two dimensional axisymmetric plasma acceleration models are built.The plasma source configuration is optimized first,in which the antenna length,location and source radius are calculated;then the equilibrium discharge and its impact factors are investigated by employing the uniform and non-uniform discharge model developed,and the plasma status varying with the radiofrequency,magnetic intensity,gas pressure is studied.In the aspect of plasma acceleration,the magnetic intensity and azimuthal velocity of magnetic nozzle is investigated first,and then the plasma acceleration of inductive pulsed plasma is discussed.The calculation of helicon discharges shows that the plasma density raises suddenly and saturates as the rf input power is increased,which is in accordance with the experiments.As the magnetic intensity is varied,the density varies non-linearly at higher intensity in the non-uniform model,while this parameter keeps linear variation in the uniform model.The result is the revision of classical conclusion,and magnifies that the sudden raise of density with magnetic intensity is the result of non-uniform discharge.The analysis of plasma movement under the effect of magnetic nozzle shows the internal energy has strong effects on the downstream expansion,which exceeds those of magnetic intensity.The higher the internal energy,the higher the acceleration efficiency.The mainly effect of changing magnetic intensity is the ratio of plasma particles captured and escaped.The investigation of plasma acceleration on the inductive coil is mainly focused on the magnetic intensity.In low intensity case,the plasma movement is within the decouple distance and can be accelerated on the whole stroke.As the intensity increases(>0.4T),the plasma reaches the decouple distance after 1/4 circle,and the effect of coil current on the plasma is reduced,the plasma is decelerated,left behind the low density and pressure particles,and main be vacuum in extreme case.The results show the acceleration efficiency is enhanced and the specific impulse is increased at high magnetic intensity,and the thruster performance is mainly determined by the acceleration effect in the first 1/4 circle.The thesis shows that on the condition of the parameters calculated,the high efficiency ionization and acceleration of the plasma thruster can be achieved using the helicon discharge and inductive acceleration,and has the prospect of being used in the micro-satellite propulsion.