Reconstruction of the transient plume cross-section of a pulsed plasma thruster

Abstract The exhaust of a small ablative pulsed plasma thruster (PPT), fed with polytetrafluoroethylene and operated at 1000 V of discharge voltage and 6 µ F of capacitance, is characterized by means of a novel diagnostic system. The technique time-reconstructs its plume cross-sectional expansion, and consists of an array of electrostatic wire probes biased at the ion saturation regime. The two-dimensional and time-dependent ion current distribution is reconstructed from the probe data using a variable separation algorithm. The new method is valid for plumes of both unsteady and steady-operation electrical plasma thrusters. The PPT plume contains at least three distinct ion groups with different mean velocities, with the second one carrying the major part of the ion current. Spatially, the plume exhibits a single-peaked profile in the direction perpendicular to the PPT electrodes, while in the direction parallel to them it features two peaks and a greater divergence angle. A small spatial asymmetry involving a deviation of the current towards the cathode and to one of the sides of the channel is also present.