Investigation On The Electron Cyclotron Ion Source Of The Electron Cyclotron Ion Source Thrusters With Different Magnetic Circuit

An electron cyclotron resonance ion thruster(ECRIT)is composed of an electron cyclotron resonance ion source(ECRIS)and an electron cyclotron resonance neutralizer.ECRIT discharges gas to produce plasma in the magnetic field in which the electron cyclotron resonance condition is satisfied somewhere and emits ions and electrons from the plasma to produce thrust.The magnetic field inside the ECRIT,which is determined by the magnetic circuit,affects the performance of ECRIT in many aspects by influencing the processes such as the microwave transmission,the electron heating and the transportation of the charged particles.Because of the interconnections among these processes,changes in the magnetic circuit results in complex variations in the performance of ECRIT.To acquire the relationship between the magnetic circuit and the performance of ECRIT and study the affecting mechanism of the magnetic circuit,various experiment were conducted on several ECRISes with different magnetic circuit.Based on the experimental results,the effects of the magnetic circuit were summarized and analyzed.A numerical code was also developed to simulate the evolution of the plasma in the ECRISes.Based on the symmetry in the structure of the ion source,the magnetic field inside the ion source was measured to calibrate the numerical results of the magnetic field.It was found that the magnets were demagnetized to a small extend due to the compact arrangement.Then the calculation process was corrected according to the measurements and more accurate numerical results was acquired.Collision processes in the plasma inside the ion source was analyzed to decide the working regime of the electric probe in the plasma diagnostic and reduce the error caused by the magnetic field.It was found that keeping the probe axis perpendicular to the diagnosing plane,which was also an symmetry plane of the ion source,reduced the interference from the magnetic field and improved the spacial accuracy of the diagnostic.The ion sources with different magnetic circuit were tested in the discharge experiment,the diagnostic experiment and the ion beam extraction experiment.Different operational modes of the ions sources were observed in the experiments.Plasma inside the ion source concentrated in the bow shape area which corresponds to the bended magnetic bottle.There was a deep gradient in plasma density and electron temperature between the zone with high density plasma and the zone with low density plasma.The performance of the ion source with different magnetic circuit differed greatly.To understand the affecting mechanism of the microwave transmission,the electron heating and the transportation of the charged particles were analyzed.It is found that the mode transition of the ion source is caused by the coupling of the electron heating and the variation of the spacial distribution of the plasma.The plasma density in the axis zone of the ion sources dominates in the mode transition.The distance between the magnetic rings affected the electron heating and the transportration of the charged particles.The position of the magnetic rings affected the efficiency of the ion source by controlling the spacial distribution of the plasma.A parallel architecture of a PIC/MCC program was designed and implemented to simulate the transportation of the charged particles inside the ion sources.The numerical results showed the same trend as the experimental results and the theoretical analysis.