Multiply charged ions in hall thruster plasmas

Operation performance and ion beam characteristics related to multiply charged ions in 200 W class Hall thruster plasmas are studied. Our previous studies reported the propellant efficiency larger than unity^1,2 in the cylindrical Hall thruster (CHT) plasma, which may be related to the presence of multiply charged ions. In this presentation, we report the measured result of the fraction of Xe²⁺ and Xe³⁺ ions in the CHT plasma (27-31%) that is significantly larger than that in the annular Hall thruster (AHT) plasma (5-8%) under the similar operating conditions^3,4. The specific impulse and thrust are measured to be higher by 1.4 times in the CHT than those in the AHT at 300 V of the anode voltage. It is found that the high values of specific impulse and thrust are related to the high fraction of multiply charged ions and high ionization rate in the CHT. The details of the comparison of the overall performance and beam characteristics associated with multiply charged ions in the AHT and CHT are presented. The large effect on the fraction of multiply charged ions due to the different magnetic field configuration with different coil current directions in the CHT plasma will also be reported.