The Effects of Cathode Configuration on Hall Thruster Cluster Plume Properties

Abstract

Clusters of Hall thrusters are being considered for use on a variety of missions requiring electric propulsion systems capable of operating at power levels in excess of the current state of the art. One of the key factors to be considered in determining the optimum cluster architecture is the configuration of the electron-emitting cathode(s). This work presents experimentally determined plume properties and discharge current characteristics obtained with multiple thrusters coupled to a single cathode. Spatially resolved plasma density, electron temperature, and plasma potential data are presented during both single thruster and cluster operation. Measurements taken in this configuration are compared to previously published data obtained with each thruster coupled to its own independent cathode. Significant differences between the two configurations are noted and explained. Additionally, critical plasma parameters in the cluster plume are shown to be strongly influenced by the location of the hollow cathode. Clusters of Hall thrusters are being considered for use on a variety of missions requiring electric propulsion systems capable of operating at power levels in excess of the current state of the art. One of the key factors to be considered in determining the optimum cluster architecture is the configuration of the electron-emitting cathode(s). This work presents experimentally determined plume properties and discharge current characteristics obtained with multiple thrusters coupled to a single cathode. Spatially resolved plasma density, electron temperature, and plasma potential data are presented during both single thruster and cluster operation. Measurements taken in this configuration are compared to previously published data obtained with each thruster coupled to its own independent cathode. Significant differences between the two configurations are noted and explained. Additionally, critical plasma parameters in the cluster plume are shown to be strongly influenced by the location of the hollow cathode.

Effect of the Hollow Cathode Heat Power on the Performance of an Hall-Effect Thruster

“…The magnetic field is weak on the plasma bridge. For the plasma parameters of n e ∼ 10 16 m −3 and T e ∼ 5 eV [6,8] , the Debye length is about 0.1 mm. Then a single Langmuir probe with its diameter chosen close to the local sheath thickness, about 10 times the Debye length, is appropriate for the measurements of the space potential of the plasma bridge.…”

“…To that end, the experimental data in Ref. [8] are adopted, namely, n = 1×10 18 m −3 , U s = 20 V, T e = 1 eV and T = 1800 K. The result is.…”

“…ALBAREDE et al compared the effects of three kinds of thermionic orifices on the HET performance and noticed that the oscillation frequency of the HET discharge current varied with the HC mass flow rate [7] . BEAL B E et al further studied the HET plume characteristics by assembling different HETs and HCs, and measured the plasma parameter distributions in the plume [8] . By fixing the HC in different positions, HOFER R R et al found that the HC coupling voltage (the potential of HC relative to ground) is the lowest when the cathode is placed on the central axis of HET [9] .…”

Air Force Research Laboratory High Power Electric Propulsion Technology Development

“…The thruster performance and plume will be characterized for several operating configurations and power levels. performance operation with multiple cathodes or in a singleshared cathode configuration [4]. However, the local plasma properties may be affected in certain cathode configurations.…”

“…In the study, a 200-kW PPU was estimated at approximately 0.9 kg/kW for a high-power Hall thruster propulsion system. 4 Specific mass of the NASA-457M is based on the 50-kW design point for an 80-kg thruster mass. This will be decreased if the individual thruster operating power of 67-kW is used.…”