Vacuum facility neutral flux analysis

Understanding neutral flux behavior within vacuum facilities is important for characterizing the facility effects and design. For applications such as electric propulsion (EP), thruster behavior, performance, and lifetime during ground tests are often obfuscated by facility-borne neutral particles in the thruster plume and those ingested into the thruster. To characterize dominant neutral flow phenomena within EP vacuum facilities, we use 3D flux-based angular coefficient methods to provide rapid and robust analyses. Analytical and computational modeling is used to characterize representative geometries as well as two large, state-of-the-art EP facilities. The results show that the “bulk drift” of neutral particles provides a three-dimensional motion of neutral species within vacuum facilities. Using this perspective, facility operators and designers can quantify particle fluxes and densities throughout the chamber to characterize the facility effects for ground-based thruster testing and other vacuum applications.