Cathode coupling effects on the performance of a low-power external discharge plasma thruster using a modular hollow cathode

In this work, the influence of the operating parameters and position of a modular hollow cathode neutraliser on the performance of a low-power channel-less plasma thruster is investigated. The External Discharge Plasma Thruster is coupled with a modular cathode to experimentally research changes in thruster performance due to variations in the cathode’s discharge parameters like additional heating, different keeper currents, and mass flow rate. As the cathode is closer to the anode, the cathode-to-ground potential increases (lower in magnitude) and the keeper voltage decreases (decrease in cathode power). Increasing the emitter temperature by an additional 120 W increases the cathode-to-ground voltage, lowers the plasma potential, and increases electron density, indicating a reduced plasma resistivity in the coupling region. Varying the cathode mass flow rate from 0.1 to 0.3 mg/s increases the electron density, while the plasma potential and electron temperature decrease in the coupling region. The ion beam profile reveals that the beam current increases as the cathode mass flow rate is raised from 0.1 to 0.3 mg/s. Increasing the cathode mass flow rate reduces the total power (cathode and anode combined), but increases the anode’s power contribution, leading to comparable anode efficiencies and thrust-to-power ratios for both cathode operations. • Miniaturised channel-less Hall thruster developed to address channel erosion issues. • Peak thrust of 12.6 mN achieved at 350 W anode power and 1.2 mg/s mass flow rate. • Cathode coupling effects on thruster performance and plasma properties are examined. • Additional emitter heating increases electron emission and thruster performance. • Beam current and utilisation efficiency improve with increased cathode flow rate.