Modelling of ion thruster plumes for spacecraft contamination

Summary form only given. The authors have developed a 2-D electrostatic hybrid plasma particle-in-cell code with a Monte Carlo collision operator to simulate the transport of ions in the plume of an ion thruster. The electron density, velocity, and temperature are computed by solving the electron continuity, momentum, and energy equations. All ions move under a self-consistent potential field computed from the ion and electron densities with Poisson´s equation. Charge-exchange (CEX) collisions between beam ions and neutrals are modelled with a Monte Carlo collision operator. The CEX plasma is created from interaction between slow neutrals and fast ions (of species from both the propellant and sputtered metals) which can expand and propagate back towards a spacecraft, and hence presents a contamination problem that must be well understood. Preliminary results on the plume flow structure such as density and potential contours have been obtained.