Thrust measurements of a waveguide electron cyclotron resonance thruster

Abstract

Direct thrust measurements are performed on a circular waveguide electron cyclotron resonance (ECR) thruster working at 5.8 GHz using a pendulum thrust balance with mechanically amplified displacement. Thrust levels between 1 and 3.5 mN are found for power levels in the range of 60–350 W and xenon flow rate between 2 and 8 SCCM. A maximum thrust efficiency of 3.5% is reached at 2 SCCM and 60 W. Plasma plume diagnostics are used to estimate the thruster partial efficiencies to understand the main losses, and to perform a comparative analysis between directly and indirectly measured thrust. Results suggest that the low energy conversion efficiency and propellant utilization efficiency (<6.4% and < 53%, respectively) are the key factors spoiling the ECR thruster performance. Finally, retarding potential analyzer measurements show the presence of energetic electrons with energy tail up to about 300 eV.