Effect of anode configuration and material on discharge erosion and plasma behavior in pulsed plasma thrusters

Electric propulsion is essential for miniature satellites to perform precise maneuvers, with particular attention to plasma plume behavior and its harmful effects on spacecraft subsystems. This study investigates the impact of asymmetric anode configuration and material on discharge characteristics, plasma morphology, magnetic field distribution, electron density, and erosion of a 2.5 J pulsed plasma thruster. Three anode types were tested: standard copper anode (20 mm), short copper anode (5 mm), and short tungsten anode (5 mm). Diagnostics included thrust measurements, high-speed imaging, a triple Langmuir probe, magnetic field mapping, scanning electron microscopy, and optical emission spectroscopy. The short tungsten anode achieved the highest impulse bit of 78 μN s at 1500 V, approximately 7% higher than short copper and 12% higher than standard copper. High-speed imaging revealed a brighter and more concentrated plasma plume with enhanced electromagnetic acceleration and reduced turbulence. Magnetic field measurements confirmed the strongest localized self-induced field in the short tungsten configuration, peaking at 1.3 μs. Electron density profiles demonstrated better plasma uniformity and ionization from initial breakdown (1 μs) to steady state (3 μs). After 15,000 discharges, the short tungsten anode exhibited the lowest erosion rate (0.10 μg/discharge) and highest mass bit (8.9 μg/shot). Scanning electron microscopy confirmed minimal surface degradation of the tungsten anode compared to significant melting, pitting, and resolidification observed on copper anodes. Optical emission spectroscopy verified plasma composition dominated by propellant-derived species. The experimental results provide a reference for anode optimization strategies to improve pulsed plasma thruster performance and durability.