Endurance-test and theoretical prediction of a rare earth nanocathode for the applied field magnetoplasmadynamic thruster

The erosion loss of cathode is essential for the lifetime of magnetoplasmadynamic thruster (MPDT). In this work, an endurance test system for MPDT cathodes was designed and developed, and the erosion characteristics, erosion rate and erosion mechanism of the cathode were studied using the system under vacuum condition. The WCe20 hollow cathode was selected to carry out the long-term erosion of 540 h with the argon propellant supply flow rate of 40 ml min⁻¹, the input current of 25 A, and the central magnetic field intensity of 96 Gs. In order to predict the theoretical service life of cathode, a steady state erosion numerical model was established. The calculation results show that the total erosion rate of sputtering and evaporation is 11.58 mg h⁻¹, which is slightly smaller than the test data of the average cathode corrosion rate of 12.70 mg h⁻¹ in the experiment, because the experimental value includes start-up erosion rate.