We report sputtering studies of multi-component spacecraft materials. We employ two complementary diagnostic methods: weight loss measurements and cavity ringdown spectroscopy (CRDS). The weight loss measurements provide total sputter yields as a function of ion energy and incidence angle. We present sputter yields from weight loss measurements for xenon ion sputtering of molybdenum, quartz, boron nitride, and kapton. The CRDS provides species-specific sputtering data (number density and velocity) as well as information on the differential (angular) sputtering distributions. We present CRDS results for the sputtering of molybdenum (from a molybdenum sample), and demonstrate measurements of multi-component materials by measuring the sputtering of chromium, iron, and molybdenum from inconel 718.

Hollow cathodes are used in plasma contactor and electric propulsion devices to provide electrons for sustaining plasma discharges. Based on previous cathode life tests where erosion was observed on hollow cathode assembly components, it is desirable to understand the plasma flow field downstream of hollow cathodes. Plasma flow field measurements are presented herein for hollow cathode generated plasmas using both local and remotely located plasma diagnostics. Two cathode discharges are presented: 1) an open, no magnetic field configuration and 2) a setup simulating an ion thruster discharge chamber. In the open cathode configuration, large amplitude plasma potential oscillations, ranging from 20 V to 85 V within a 34 V discharge, were observed using a floating emissive probe. These oscillations were observed over a dc potential profile that contained a clear potential hill structure. A remotely located electrostatic analyzer (ESA) was used to measure the energy of ions produced within the plasma, and energies were detected that met and in some cases exceeded the peak plasma potentials detected by the emissive probe. In the prototype NSTAR-like discharge chamber configuration, plasma potentials from the emissive probe agreed with ion energies recorded by the remotely located ESA. A correlation model was used to compare the local and remote measurements in both cathode discharges. Nomenclature

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