Theory of RF Plasma Cathodes and Supporting Experiments for Electric Propulsion Applications

A sheath theory for RF plasma cathodes is developed based on an analogy with asymmetric double probe. It is shown that the family of curves produced is expected to collapse onto a single curve under a normalization of the discharge current to the ion saturation current and the discharge voltage to the electron temperature. This theory is combined for a global model to numerically study anticipated performance trends in an Ar discharge. These simulations are followed with experimental measurements of a cathode using Ar. The theory is shown to capture qualitative experimental trends, notably the collapse of the current-voltage curves onto a single curve under normalization. A quantitative comparison between theory and experiment is conducted and shows good agreement for key operating parameters such as discharge voltage and current.