Research On Grid-controlled Particle Source Based On Radio Frequency Plasma

Radio frequency ion source adopts the form of electrodeless discharge,which has the characteristics of long service life,large uniform area and small pollution.The ion beam formed by it is widely used,especially in the field of ion electric propulsion.Therefore,radio frequency ion thruster is considered to be one of the most ideal space thrusters in the future.The gas discharge and beam extraction in the discharge chamber are the focus of the research of RF ion thruster.Therefore,the main research contents of this thesis include:The RF inductively coupled plasma is simulated by finite element simulation software.A series of plasma parameters are obtained and analyzed under Maxwell electron energy distribution function,including electron density distribution,electron temperature distribution,sheath,plasma potential distribution and induced electromagnetic field distribution.The effects of gas pressure and RF input power on plasma parameters are studied.Under the influence of background gas flow,the spatial morphology distribution of charged particles and neutral particles are analyzed.In order to get more accurate simulation at low pressure,the electron energy distribution function under this condition is obtained by using the two term Boltzmann approximation method,and coupled to the plasma fluid model for simulation.It is found that there is little difference in electron energy distribution and electron density distribution under certain conditions.The ion optical system and focusing system are simulated by using the sheath emission model and trajectory tracking module in PIC simulation software.The parameters of the double grid ion optical system are determined through simulation and debugging.An immersion lens focusing pole with gradient structure on the left side is designed and compared with the non equal diameter immersion lens focusing pole under the same scale parameters.The results show that compared with the latter,the minimum radius of the ion beam after focusing by the former is not much different,but the length of the smooth area of the ion beam is 26 mm higher,and the maximum energy of the ion beam is 357 e V higher.The preliminary experiments of RF inductive coupling discharge and beam extraction were carried out.The relationship between stable ignition power under different gas flow rates was obtained,and the phenomenon of E-H mode conversion discharge was observed.A series of relationships between the beam size and the extraction voltage are obtained by using the method of double grid extraction of ion beam,non grid extraction of electron and ion beam and single acceleration grid extraction of ion beam.At the same time,it is found that the extracted beam size is basically at the level of m A and the corresponding calculated thrust is at the level of μN.