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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. [ABSTRACT FROM AUTHOR]

A circular waveguide electron cyclotron resonance plasma thruster prototype driven by microwaves at 5.8 GHz (80–300 W) is characterized. The magnetic field is generated by a combination of Sm-CoYXG32 magnets and an electromagnet, which enables the tuning of the resonance position and magnetic nozzle shape. The main plasma plume properties are analyzed by using electrostatic probes when the mass flow rate (Xenon), microwave power, electromagnet current, and propellant injector design are varied. An estimation of the propulsive performance of the device is also presented. Results show that a single radial injector hole is not sufficient for a symmetric ion current profile and that magnetic nozzle shape and strength tuning can significantly affect the divergence angle and thruster floating potential. A utilization efficiency of up to 70% and electron temperatures of up to 16 eV have been measured. [ABSTRACT FROM AUTHOR]