Title: Particle-in-cell simulations of the ion extraction and acceleration processes in the alternative low power hybrid ion engine (ALPHIE)
Authors: J. Gonzalez and L. Conde
Date of publication: April 8th 2019
Journal: Proceedings of the 32th International Electric Propulsion Conference, IEPC
DOI: https://doi.org/10.1063/1.5084242
Abstract: The electric charge transport through the two-grid systems of the Alternative Low Power Ion Engine is studied using a particle-in-cell (PIC)
code. In this plasma thruster design, the ionizing electrons from the only cathode and the ions extracted from the ionization chamber flow in
opposite directions through the open spaces of its grids. This configuration differs from classical gridded ion engines where only positive
ions are accelerated. The electric charge transport is simulated, and the results are in agreement with previous experimental observations.
The numerical simulations are performed for a single beamlet domain in a 2D axial symmetry, and only two aligned holes of the grid system
are studied. The extracted ions move outwards from the ionization chamber reaching supersonic velocities of 43–51 km/s which are con-
trolled by an acceleration voltage. The ionizing electrons from the only cathode are accelerated along the opposite direction and achieve ener-
gies in the range of 400–600 eV inside the ionization chamber. Additionally, the PIC simulations predict the development of an electric field
close to the exit section of the thruster not observed previously because of the practical limitations of experiments. The imbalance of electric
charge in the region where the electrons are injected from the only cathode creates a positive field that further accelerates the electric charges,
preventing low energy ions from the plasma stream from returning to the plasma thruster.