Influence mechanism of Martian atmospheric conditions on the α and γ modes transition of CO2 radio frequency capacitive coupled plasma

Radio Frequency Capacitive Coupled Plasma (RF-CCP) typically operates in two common modes:α and γ. This paper investigates the influence of the Martian atmospheric conditions, specifically gas pressure(0.5 kPa - 2 kPa) and impurity Ar(0 to 50 %), on the transition between these two modes, and further explains the underlying transition mechanism through numerical simulation models. The results indicate that with the increase of gas pressure, the mean free path of particles decreases, leading to a decrease in the drift velocity of positive ions, which in turn reduces the deposition energy of positive ions and increases the transition voltage from α mode to γ mode. After the introduction of Ar into CO2, the electron density of the plasma increased, the sheath thickness decreased, and the average electric field strength within the gap was enhanced. At the same time, the higher mobility of Ar+ compared to CO+ 2 increases the drift rate of positive ions, leading to an increase in the deposition power of positive ions with an increase in the ratio of Ar addition, and therefore a decrease in the transition voltage of the α-γ mode after mixing Ar. The findings will help to the future utilization of RF-CCP α and γ modes for CO2 conversion in the Martian environment.