Cathode phenomena in a low-power magnetoplasmadynamic thruster

Mass-loss and surface-temperature measurements, filter photography, and scanning electron microscope surface characterization were used to study cathode phenomena in a steady-state, self-field magnetoplasmadynamic thruster operated at power levels between 15 and 30 kW. The steady-state cathode temperature was found to be above 3000 K over most of its length, and evaporation and simple thermionic emission adequately explained the measured erosion rates and current levels. The steady-state cathode power balance was dominated by electron cooling and radiation. The arc ignition phase was found to last approximately 2 s and was characterized by spot current attachment with associated high erosion rates.