ホールスラスタの推進効率および内部効率に与える磁場特性の影響

Abstract

The effects of magnetic field strength and shape on thrust efficiency of a Hall thruster were examined experimentally using the THT-IV 1-kW-class Hall thruster. Thrusts were measured with varying magnetic field and channel geometry. Exhaust ion beam measurement was also implemented to evaluate internal efficiencies of propellant utilization efficiency, acceleration efficiency, voltage utilization efficiency and beam focusing efficiency. Spatial ion current profiles were measured with a Faraday probe and ion energy distribution functions were estimated from data with a retarding potential analyzer. Stable operation was obtained over the wide range of operational condition, and voltage utilization efficiency and beam focusing efficiency were estimated suitably. Acceleration efficiency and propellant utilization efficiency, however, were not able to be evaluated experimentally because the total ion current calculated by integrating the ion current density over the measured area was very small. Using obtained results, the relationships between each internal efficiency and thrust performance and between magnetic field characteristics and thrust efficiency were discussed. Consequently, it was expected that the change of magnetic field strength mainly affected acceleration efficiency and voltage utilization efficiency, and that the change of magnetic field shape affected voltage utilization efficiency in long discharge channel case and beam focusing efficiency in short channel case.