Propagating an Electrospray Emission Model to Array Scales Using Particle-in-Cell

Abstract

A multiscale approach to multi-emitter electrospray-ion source modeling has been developed to propagate emission site conditions into spatial domains viable for plume evolution simulations. This framework uses the particle-in-cell method to maintain a feasible computational complexity for consumer-grade hardware. Source models for individual emission sites are informed by an n-body single-emitter model. Molecular effects such as ion-cluster fragmentation are included. This model is used to predict array-level properties such as plume divergence angle, and to demonstrate the computational feasibility of modeling many emitters in parallel. This framework is used to quantify the relationship between array dimensions and space-charge- induced beam divergence. It is shown that including interparticle forces in plume expansion results in an increase in plume half angle by 8.1 deg for 80% and 9.8 deg for 90% of the emitter current for a commercial electrospray thruster. These data indicate that, at the array scale, space charge has a significant effect on plume evolution and must be considered in analysis of these systems.