Electrospray Propulsion Time-of-Flight Secondary Ion Mass Spectrometry Diagnostic (2411.09474v1)

Abstract: The design and capability of a novel time-of-flight secondary ion mass spectrometry electrospray propulsion diagnostic is presented to investigate secondary species emission from surface impingement of high-velocity, energetic molecular ion plumes. Designed on the basis of traditional Secondary Ion Mass Spectrometry (SIMS) principles, this diagnostic provides information on the relative intensity and chemical composition of secondary species given electrospray operational parameters like incident angle, primary ion energy, and target surface composition. The system consists of an externally-wetted tungsten ion source operating with room temperature ionic liquid propellant, a target with a secondary species extraction mesh, and a time-of-flight mass spectrometer featuring an electrostatic deflection gate and a multichannel plate detector. Results show that energetic primary plume impacts with metallic surfaces induce molecular secondary ion emission in both positive and negative polarities. Likely sources of these secondary ions are considered - including hydrocarbon contamination of the target surface and charged fragments of the molecular primary ionic liquid ions. For electrospray propulsion, these secondary species contribute not only to lifetime limiting processes intrinsic to thruster operation like impingement and thus degradation of electrodes and emitters, but also contribute to facility effects corrupting ground-based testing and thruster flight qualification.