Study on discharge characteristics of liquid metal μCAT with graphite anode

In this study, non-ablative graphite is used to replace ablative copper as the anode material in liquid metal micro-cathode arc thruster (LM-μCAT). The behavior of the anode is analyzed based on the performance parameters, discharge process and plasma plume products of the LM-μCAT. High-speed camera is used to observate the discharge process. There is localized spot ablation on the copper anode, whereas the graphite anode exhibits a strip-shaped high-temperature region. Analysis indicates the presence of copper in the plasma plume product of the copper-anode LM-μCAT, while no carbon is detected in the plasma plume product of graphite-anode LM-μCAT. It is attributed to the simultaneous evaporation of both the cathode and anode in copper-anode LM-μCAT, which causes the resistance between them to drop more rapidly and reach the breakdown threshold earlier. As a result, the voltage of breakdown arc is lower, leading to a reduced degree of plasma ionization. When copper is functioning as the anode, the material loss of copper eventually leads to anode deformation and ablation, which reduces the theoretical lifetime of the thruster.