Experimental Characterization of a Wire-Fed Metal-Propellant Hollow Cathode

The performance of a barium oxide hollow cathode on zinc propellant is compared to performance on krypton propellant. Historical metal propellant feed systems relying on sublimation or boiling struggle with propellant metering and scalability for flight systems. This study demonstrates a wire-feed system for zinc delivery and measures anode current-voltage characteristics, plume Langmuir probe data, and oscillations in discharge current at 10 sccm and 15 sccm of zinc and krypton flow. It is found that anode coupling voltages are approximately 50% lower for zinc than for krypton and this is attributed to a lower resistivity of the plasma with zinc propellant. It is also found that the zinc plasma is more quiescent for the same operating conditions compared to operation with krypton. These findings ultimately show that the response of the cathode with zinc is not outside family for cathode operation on noble gases, providing a promising path forward for the option of this propellant for Hall thruster operation.