Evaluation of Ionization Efficiency in a Carbon Dioxide Hall Thruster by 0-D Discharge Simulation

Xenon has been typically used as a propellant for Hall thrusters. Its characteristics are its high relative density and low ionization cost. On the other hand, there are disadvantages such as increased tank weight owing to high storage pressure and high costs. Therefore, perspective of ISRU (In-Situ Resource Utilization) during Mars exploration, JAXA and Nagoya University have proposed CO2 as an alternative propellant. However, its plasma characteristics have not been fully understood, and it is necessary to understand by numerical calculation. Since CO2 is a molecule, various ions are produced when it is used as a propellant. Ionization other than CO2+ is costly and causes energy loss, reducing thrust performance. Thus, it is necessary to perform collision calculations using the electron temperature as a parameter to estimate the region where a large amount of CO2+ is produced. In this paper, we perform a non-dimensional PIC simulation to estimate the electron temperature to maximize the degree of ionization of CO2+. As a result, it was found that the optimum electron temperature for CO2 operation is about 15 eV.