Investigation on horizontal asymmetries in plasma plume of a pulsed plasma thruster

This study investigates the horizontal asymmetry of plasma plumes in a pulsed plasma thruster (PPT), focusing on the distribution of electron density and magnetic field strength. Using a triple Langmuir probe, the electron density was measured, revealing a peak density on the right side that was up to 87 % higher than the left side at representative points. Concurrently, magnetic field measurements using a magnetic probe revealed a non-uniform distribution, with the strongest disparities localized near the electrodes during current reversal, exhibiting a 59.11 % higher magnetic field strength in these areas. These magnetic asymmetries were identified as the primary driver of the observed plume canting, influencing the Larmor radius of charged particles and inducing trajectory differences. The experiments demonstrated repeatability errors of 7.43 % for Langmuir probe data and 34.79 % for magnetic probe measurements, confirming the reliability of the results. The findings highlight that plume canting originates from non-uniform Lorentz forces caused by asymmetric magnetic fields near the electrodes. This phenomenon results in a preferential plasma flow direction, leading to risks of component contamination and reduced thruster efficiency. Additionally, plasma backflow was observed traveling at approximately 5 km s⁻¹, occurring approximately 10 µs after the discharge and lasting for 4µs on both sides of the thruster, further contributing to potential contamination risks. These results underscore the importance of accounting for horizontal asymmetry in PPT designs and suggest that optimizing the magnetic field distribution could improve thruster performance.