Experimental measurements of Colloid Thruster plumes in the ion-droplet mixed regime

Abstract

Under the right conditions, colloid thruster plumes may be composed of a mixture of ions and droplets. Experimental techniques, including time-of-flight and stopping potential measurements are used to characterize plumes with large ion fraction. The energy distribution of these beams is very rich, indicating that individual components have different energies. Electrostatic focusing with an einzel lens is used to selectively observe charged particles that share a range of energies. Formamide doped with NaI is used as propellant. Measurements show that Na+ with 7 formamide molecules solvated on it is likely to be the ion emitted from the cone-jet structure. The remainder of the current in the beam is taken by droplets with a relatively high dispersion in specific charge.