Development of a Plasma Chemistry Model for Helicon Plasma Thruster analysis

The present work is part of a wider project aimed at improving the description of the plasma dynamics during the production phase of a Helicon Plasma Thruster. In particular, the work was focused on the development of a chemical model for Argon- and Xenon-based plasma. The developed model consists of a collisional radiative model suitable to describe the dynamics of the 1s and 2p excited levels. The model is meant to be complementary to 3D-VIRTUS, a numerical tool which enforces a fluid description of plasma, developed by the University of Padova to analyse helicon discharges. Once identified, the significant reactions for both propellants, the reaction rate coefficients, have been integrated exploiting cross sections from literature and assuming a Maxwellian velocity distribution function for all the species. These coefficients have been validated against experimental measurements of an Argon Inductively Coupled Plasma and compared with a well-established code. For Argon, the selected reactions have been reduced through a proposed lumping methodology. In this way, it was possible to reduce the number of equations of the system to solve, and implement them into 3D-VIRTUS. A validation against an experimental case taken from literature was performed, showing good agreement of the results. Regarding the Xenon model, only a verification has been performed against the results of another collisional-radiative model in literature. Finally, a predictive analysis of the propulsive performances of a Helicon Plasma Thruster for both Argon and Xenon is presented.