Angular Properties of Ionic Liquid Electrospray Emitters

Abstract

The angular distribution of emitted species in electrospray ion beams is not well characterized and can have negative effects on propulsive performance and emitter lifetime. We present an experimental characterization of the angular distribution of emitted species in a single electrospray ion beam as a function of firing voltage using time of flight mass spectrometry. Angular current distributions indicate the central axis of emission varies up to 10 degrees from the central axis of the emitter tip. Variation in the ion species as a function of angle depends on the firing voltage. Simulations of single particle trajectories indicate that fragmentation of ion clusters results in ion products moving closer to the center of the beam and neutral products spreading up to 47 degrees depending on how rapid fragmentation occurs. Experimental results are compared to multiscale full-beam simulations of electrospray emission and future use of these simulations to explain angular beam behavior is discussed.