HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Direct thrust measurements have been performed on a low-power (30 W) ECR plasma thruster operated with xenon. The total thrust, the force exerted on the walls of the source (thermal thrust), and the force exerted on the permanent magnet (magnetic thrust) have been measured separately for various operating conditions (power and flowrate). The results are compared for two magnetic field topologies (with a different magnetic field gradient and divergence). The magnetic thrust dominates thermal thrust for most operating conditions, and its contribution to total thrust can be as high as 80%. A saturation of magnetic thrust with increasing power has been observed and is correlated with a decrease in thrust efficiency. A high degree of electron anisotropy can be inferred from the thrust measurements.

Electrostatic probe and thrust balance measurements of a coaxial electron-cyclotron-resonance plasma thruster with magnetic nozzle are compared against numerical simulations of the device that solve self-consistently the plasma transport problem with a hybrid particle-in-cell/fluid approach and the microwave electromagnetic fields using mixed finite elements. A simple phenomenological anomalous transport model similar to those used in Hall thruster modeling is applied. Reasonable average relative errors are reported on the ion current density (8.7%) and plasma density (12.8%) profiles along the plume. Good agreement is found in terms of relative errors on thruster performance parameters as the 90%-current divergence angle (0-3%), utilization efficiency (3-10%), peak ion energy (9-15%), and energy efficiency (2-17%). The comparison suggests that enhanced cross-field diffusion is present in the plasma. Differences in the experimental and numerical behavior of electron temperature point to the areas of the model that could be improved. These include the electron heat flux closure relation, which must correctly account for the axial electron cooling observed.