Passive optical diagnostic of Xe-propelled Hall thrusters. I. Emission cross sections

This paper presents a set of xenon apparent emission excitation cross sections for emission lines that have diagnostic value in the analysis of Xe-propelled Hall thruster plasmas. Emission cross sections are presented for three excitation processes involving ground-state xenon atoms: e−+Xe, Xe++Xe, and Xe2++Xe. The cross sections are derived from luminescence spectra produced at single-collision conditions. Apparent emission excitation cross sections are tabulated for 12 visible and 8 near-infrared lines for electron energies ranging from 10to70eV. In case of the near-infrared lines, radiation trapping effects are accounted for by measuring the detailed pressure dependence of the apparent emission cross sections and extrapolating to zero pressure. A semiempirical expression for the pressure dependence is derived that allows zero-pressure extrapolation from threshold to 70eV. Ion-induced cross sections are reported for the same emission lines at an energy per unit charge E∕q of 300eV, chosen for typical Hall thruster operating voltages. Radiation trapping effects are negligible for the ion emission excitation cross sections between 0.1 and 2.0mTorr in the present luminescence experiment.