Published differential cross section data for heavy particle collisions between xenon ions and neutral xenon has been incorporated into plasma simulations for electric propulsion modeling. A fit has been made to the published data in order to estimate the relative contribution from charge exchange and elastic collisions and to reduce the computational cost of utilizing the differential cross section in existing numerical models. Since the published profiles do not include scattering data near 0 degrees, the differential cross section was assumed to be constant at low angles. The angle at which the differential cross section was assumed to transition from the constant profile to the fit was chosen such that the differential cross section integrated to the published total cross section value for xenon scattering. In order to make the resulting differential scattering curve generally applicable to other types of collisions with dissimilar collision partners, the profile was converted from the laboratory frame into center of mass coordinates. Each time a scattering event was determined to take place in the electric propulsion modeling codes, a scattering angle of the incident particle was chosen using a cumulative distribution function. The behavior of the target particle was determined using conservation of energy and momentum.
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.
We present the application of laser-induced fluorescence of singly ionized krypton as a diagnostic technique for quantifying the electrostatic acceleration within the discharge of a laboratory cross-field plasma accelerator also known as a Hall effect thruster, which has heritage as spacecraft propulsion. The 728.98 nm Kr II transition from the metastable 5d(4)D(7/2) to the 5p(4)P(5/2)(∘) state was used for the measurement of laser-induced fluorescence within the plasma discharge. From these measurements, it is possible to measure velocity as krypton ions are accelerated from near rest to approximately 21 km/s (190 eV). Ion temperature and the ion velocity distributions may also be extracted from the fluorescence data since available hyperfine splitting data allow for the Kr II 5d(4)D(7/2)-5p(4)P(5/2)(∘) transition lineshape to be modeled. From the analysis, the fluorescence lineshape appears to be a reasonable estimate for the relatively broad ion velocity distributions. However, due to an apparent overlap of the ion creation and acceleration regions within the discharge, the distributed velocity distributions increase ion temperature determination uncertainty significantly. Using the most probable ion velocity as a representative, or characteristic, measure of the ion acceleration, overall propellant energy deposition, and effective electric fields may be calculated. With this diagnostic technique, it is possible to nonintrusively characterize the ion acceleration both within the discharge and in the plume.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.