Purpose and Objectives
Solutions to vacuum chamber particle-contamination are being sought to reduce uncertainties during electric propulsion (EP) ground testing. This research presents a geometric design and optimization technique for beam targets – the primary source of contamination during EP testing – to support EP development.
Methods
University of Michigan’s radially symmetric test chamber was modeled in COMSOL Multiphysics’ mathematical particle tracing module. Ten thousand emitted particles follow a HERMeS hall-effect thruster plume profile from the thruster to the beam target (BT). A pre-optimization BT geometry was determined through a specular-reflection analytical model. At each point of interaction with the BT, COMSOL reads a probability matrix from the ion-irradiation software, TRI3DYN, to statistically determine the trajectory of xenon reflections from a flat carbon surface. After several optimization iterations, a BT design was selected and compared to UM’s BT with the objective function of maximizing particle concentration at pumps located on the chamber’s back wall.
Results
An optimized beam target orientation and geometry increased particle concentration to the back pumps by 57.6%. Near-specular behavior of xenon reflections was verified between molecular dynamic (MD) simulations from literature and these TRI3DYN results, permitting acceptable use of an analytical reflection model for pre-optimization design
Conclusions
A beam target optimization technique is presented which enables BT designs for high-concentration back-wall- pumping of contaminating particles. Both simulations that use the binary collision approximation and molecular dynamics display reflection trends that are suggested by empirical findings in the literature. This research presents capabilities with TRI3DYN and COMSOL cooperation, enabling first-order BT optimization.