Plasma Properties in the Plume of a Hall Thruster Cluster

Abstract

The Hall thruster cluster is an attractive propulsion approach for spacecraft requiring very high-power electric propulsion systems. Plasma density, electron temperature, and plasma potential data collected with a combination of triple langmuir probes and floating emissive probes in the plume of a low-power, four-engine Hall thruster cluster are presented. Simple analytical formulas are introduced that allow these quantities to be predicted downstream of a cluster based solely on the known plume properties of a single thruster. Nomenclature A = area of one electrode AS = surface area of sheath surrounding an electrode B = magnetic field strength E = electric field strength e = electron charge kb = Boltzmann’s constant me = electron mass mi = ion mass n = electron number density n0 = reference density Te = electron temperature Te,0 = reference electron temperature Vd2 =v oltage measured between triple probe electrodes 1 and 2 Vd3 =v oltage applied between triple probe electrodes 1 and 3 V f = floating potential γ = ratio of specific heats δ = sheath thickness λD = electron Debye length φ = plasma potential φT = thermalized potential Subscript j = contribution from an individual thruster