The effects of clustering multiple Hall thrusters on plasma plume properties
Clusters of Hall thrusters have been proposed as a means of achieving electric propulsion systems capable of operating at very high power levels. To facilitate testing in existing vacuum facilities, initial tests have focused on a cluster of low-power Busek BHT-200-X3 Hall thrusters. A combination of triple Langmuir probes and floating emissive probes is used to study the effects of multi-thruster operation on the electron number density, electron temperature, and plasma potential in the plasma plume. The resultant number density is shown to be a result of linear superposition of the plumes of individual thrusters, while the electron temperature in the cluster plume is measured to be slightly higher than that caused by operation of a single thruster. The plasma potential downstream of the cluster is shown to obey the Boltzmann relation. In the region between the thrusters, the plasma potential increases as a function of downstream distance and may result in reflection of some low-energy charge exchange ions back toward the cluster. A mechanism that may lead to slightly reduced ion beam divergence through focusing of ions directed toward the thruster centerline is discussed. © 2003 by Brian Beal.
