The Effect of Magnetic Field on the Performance of Low-Power Cylindrical Hall Thrusters

The annular design of the conventional Hall thruster does not naturally lend itself to scaling to low power. The efficiency tends to be lower, and the lifetime issues are more aggravated. Cylindrical geometry Hall thrusters have lower surface-to-volume ratio than conventional annular thrusters and, thus, seem to be more promising for scaling down. The effect of the magnetic field on the discharge characteristics and efficiency of the low- power cylindrical Hall thrusters with channel outer diameters of 2.6 cm and 3 cm was investigated. The thrust measurements were conducted at the Electric Propulsion and Plasma Dynamics Laboratory (EPPDyL, Princeton University). The thrust stand operation at low applied thrust and the accuracy of thrust measurements were studied in detail through the comparison of several calibration and measurement techniques. To achieve a sufficient accuracy of measurements, special calibration and measurement procedures were developed. The experimental results demonstrate that the enhancement of the axial component of the magnetic field in the cylindrical thruster leads to the increase of the thruster efficiency. A substantial flexibility in the magnetic field configuration of the cylindrical thruster is a key tool in achieving the high-efficiency operation. The electron confinement and ion acceleration can be optimized over a family of realizable magnetic field distributions.