Determination of the Beam Divergence of a Gridded Ion Thruster Using the AEPD Platform

At the Leibniz Institute of Surface Engineering (IOM), an advanced electric propulsion diagnostic (AEPD) platform has been set up for comprehensive in-situ characterization of EP thrusters. The platform utilizes a five-axis positioning system and several diagnostic tools for particle beam characterization, optical inspection and thermal characterization. The modular design of the AEPD platform allows very flexible adaption to different vacuum chambers, different EP thruster types, and test campaign requirements. Recently, the portfolio of diagnostic tools was extended by a multi-sensor semi-circular arc. Currently, it is equipped with 15 Faraday probes. Thus, it can be used for quick determination of the beam divergence of a thruster. The arc is mounted vertically and can be rotated in the horizontal plane. In this way, 15 horizontal beam current density profiles can be acquired in a single scan allowing for a full 2D-map of the beam current distribution for a given distance of the arc from the thruster exit plane. The data can also be used to determine the thrust vector. In addition, a simulation tool for determining the ion current density profile for gridded ion thrusters was developed which allows a direct comparison with the measured current density maps. Furthermore, the simulation tool allows to optimize the design of the extraction grid system according to specific requirements, for instance, in order to minimize the interaction of the ion beam with thruster or satellite components.