PIC modeling of iodine plasma for electric propulsion conditions

With xenon, the foremost propellant for electric spacecraft propulsion, getting scarcer and more costly, some satellite manufacturers have moved to more easily sourced noble gases, such as krypton. However, these alternative propellants have the drawback of a poorer energy efficiency, as their ionization energies are higher and ion masses lower. Iodine is a promising alternative thanks to its close physical properties to xenon.

However Iodine plasma chemistry may impact performances in ways that may be difficult to predict. Electron collisions with I₂ molecules introduce new energy losses and new charged species in the form of molecular and negative ions. Moreover, the cross sections of the reactions that occur in iodine plasmas are not as well benchmarked as in noble gases.

To simulate iodine plasma discharges we use a global model to first compute the expected average densities and temperatures of all species species. These parameters are given as inputs to a Particle In Cell Code with a Monte-Carlo Collision module including a detailed iodine chemistry . This method allows us to test our models and cross section sets against Langmuir probe and optical measurements conducted in low pressure iodine discharges performed in a prototype thruster at LPP.