Characterization of a very low power double stage Hall thruster using high-resolution optical and electrostatic diagnostics

In the current “New Space” era, small satellites are becoming increasingly popular due to their low launch cost. However, there is still a gap between the requirement for low power propulsion systems and the available solutions. A considerable effort is devoted to downscaling the existing popular Hall Effect Thruster (HET) to the low power available in small satellites. However, the efficiency of these devices drops dramatically with power, and significant design changes are required to allow efficient operation. A bottleneck preventing advancement is the physics of these small HETs, which can be quite different than that of classical HETs. Moreover, diagnostics of the plasma are difficult to perform due to miniature size of these thrusters.
Therefore, in this work we propose a combined approach for studying low power HETs. The spatial variation of plasma parameters in the near-field is measured using electrostatic probes and optical emission spectroscopy (OES) techniques. In particular, the ion number density, ion current density and plasma potential were measured with the probes, and the electron temperature was measured with both methods. The approach was implemented for a specific low power HET called the “Narrow Channel Hall Thruster” (NCHT) for several operating points. The electron temperature results from the different analysis approaches were compared. The validity of the OES method and the dependency in the Collisional Radiative theoretical model is discussed. The thruster behavior and loss mechanisms in the different working points are analyzed from the obtained data.