Kinetic model of a helicon plasma source for VASIMR

Abstract

Plasma kinetic model for the analysis of composition of partially ionized hydrogen gas in the helicon plasma source used in the VASIMR thruster is developed. Zero dimensional model provides a calculation of the main parameters of the helicon hydrogen discharge. It solves a set of 14 coupled non-linear plasma chemistry equations with relevant boundary conditions. To calculate mean velocity of the gas flow we use hybrid mixed-collisional pipe flow model. Numerical results are benchmarked against current VX-1 data for hydrogen, deuterium and helium discharges. They also used to explain some of the experimental observations. Next the model is used to predict helicon plasma source performance in space, including next step VF-10 configuration. The following effects are analyzed: gas pre-heating, catalytic break of molecules, role of vacuum chamber pressure and baffles to retain gas. We discuss a possibility of fully kinetic simulation of multidimensional gas flow in a channel and relative importance of various gas-plasma collisions.