Far-field plume properties of a cluster of 100 W-class permanent magnets Hall thrusters

International audienceIn this study, a cluster of two 100 W-class permanent magnets Hall thrusters is characterized in terms of plasma plume content in the large PIVOINE_2G vacuum chamber. The two thrusters have been operated with xenon as a propellant over a broad range of discharge voltages and mass flow rates, with their own 1 A-class hollow cathode. Plasma plume properties have been measured by means of a Faraday cup, a repulsing potential analyzer for both single thruster and cluster operations over a 180 • circular arc. Such measurements have been performed for two different anode spacings. The ion current density angular profiles measured in the plume of a cluster tends to be higher in the core of the plume and lower at larger angles compared to the sum of ion current density angular profiles of two single thrusters. Furthermore, efficiency analysis has revealed interesting features. The beam efficiency appeared to be lower for cluster operation. Also lower performances were found out for the two anode blocks operated in close configurations. The shape of the ion energy distribution functions measured in the plume of a cluster is comparable to the one observed for a single thruster operation. Notwithstanding, the broadening of the main peak appears to be higher for cluster operation, as the interactions between the two plumes favours elastic collisions. Also, the most probable energy remains unchanged in both mode operations while the mean energy of ions remains lower for cluster operation. A cluster of two anode blocks was also operated with a shared cathode. The cathode position clearly affects the cluster parameters by reducing the extracted ionic current and increasing the divergence at 90% (associated to an increasing of CEX) when the cathode-cluster axis distance increases