Analyses of TeflonTM Surface Charring and Near Field Plume of a Micro- Pulsed Plasma Thruster

摘要

The Teflon(TM) ablation in a micro-Pulsed Plasma Thruster is studied with an aim to understand the charring phenomena. Microscopic analysis of the charred areas shows that it contains mainly carbon. It is concluded that the carbon char is formed as result of carbon flux returned from the plasma. A simplified model of the current layer near the Teflon(TM) surface is developed. The current density and the Teflon(TM) surface temperature have peaks near the electrodes that explain preferential ablation of these areas as was observed experimentally. The comparison of the temperature field and the ablation rate distribution with photographs of the Teflon(TM) surface shows that the area with minimum surface temperature and ablation rate corresponds to the charring area. This suggests that the charring may be related to a temperature effect. Electron densities predicted by the plume model are compared with near field measurements.