A novel particle source based on electrospray charging for dust accelerators and its significance for cosmic dust studies

Abstract

In situ cosmic dust analyzers, like those aboard Cassini, Galileo, and Stardust, provide important data about cosmic dust, including the chemical composition of dust particles. Correctly interpreting the data from these cosmic dust analyzers requires laboratory calibration experiments. By studying the impact mass spectrum from a particle of known composition, an unknown particle’s composition can be inferred from its impact mass spectrum measured in situ. This work expands a recently presented method, electrospray charging, introduced as a means of charging minerals, astrophysical ices, and mineral-ice mixtures that are not electrically conductive. This overcomes a limitation of current dust accelerators: they can only charge, and therefore accelerate, electrically conductive particles. This paper presents experiments demonstrating that microparticles (typically 2 micrometers) of olivine, a common mineral in meteorites, and of an ordinary chondrite (Allan Hills A 79045) can be electrically charged even though neither is electrically conductive. This article discusses the acceleration potential of electrospray-charged projectiles, and explores ways to overcome the challenges implicit in coupling an electrospray source to a dust accelerator. Electrospray charging may enable experiments with novel projectiles that are better analogues for cosmic dust than the conductive projectiles currently in use. Theoretical charging limits using this technique would allow micron-sized particles to be accelerated to several km/s using 3 MV potential, with higher velocities for smaller particles.