A Comparison of Ion Acceleration Characteristics for Krypton and Xenon Propellants within a 600 Watt Hall Effect Thruster

摘要

There is growing interest within the electrostatic propulsion community in the use of krypton as a propellant. It is a lower cost replacement for xenon, and is especially of interest for potentially very large solar electric transfer vehicles that may potentially strain xenon production capability. This work compares the internal propellant acceleration of krypton within a laboratory medium power Hall effect thruster to historical xenon data for the same thruster. One case matched in propellant particle flux (matched volumetric flow rates) is presented. The measurements consist of laser-induced fluorescence velocimetry extending approximately the anode to 10 mm outside the thruster into plume along the center of the coaxial acceleration channel. The results show that the acceleration process for krypton is more gradual and produces a lower electric field. As a result, energy conversion is lower than xenon for this flow matched case. In addition, there is clear evidence of ionization throughout the acceleration channel. This may explain a lower performance for krypton as this particular appears to have low propellant utilization. It is not known to what extent the less oscillatory plasma and/or the lower ionization cross-section of the krypton discharge produced this difference relative to xenon.