Secondary electron emission from dielectric materials of a Hall thruster with segmented electrodes

TLDR

The discharge parameters in Hall thrusters depend strongly on the yield of secondary electron emission from channel walls. The study measured low‑energy secondary electron emission yields from various dielectric materials used in segmented‑electrode Hall thrusters. The measurements revealed that at low primary electron energies the secondary‑electron‑yield dependence deviates from standard model fits, likely due to surface‑dependent backscattering, while at higher energies power‑law or linear fits remain appropriate.

Abstract

The discharge parameters in Hall thrusters depend strongly on the yield of secondary electron emission from channel walls. Comparative measurements of the yield of secondary electron emission at low energies of primary electrons were performed for several dielectric materials used in Hall thrusters with segmented electrodes. The measurements showed that at low energies of primary electrons the actual energetic dependencies of the total yield of secondary electron emission could differ from fits, which are usually used in theoretical models. The observed differences might be caused by electron backscattering, which is dominant at lower energies and depends strongly on surface properties. Fits based on power or linear laws are relevant at higher energies of primary electrons, where the bulk material properties play a decisive role.