Azimuthal magnetic field gradient effects on the performance and stability of a 5 kW Hall effect thruster

Abstract

Hall effect thruster (HET) component manufacturing defects can result in non-uniformities in the plasma plume, significantly affecting thruster performance. The present work quantifies the effect of an azimuthal magnetic field gradient on the thrust, stability, and efficiency of a 5 kW HET. The study introduces an azimuthal magnetic field gradient inside the discharge channel of the P5, a 5 kW HET, through modifications of the outer magnetic coil circuit to simulate the impact of a manufacturing defect in the magnetic circuit. Far-field plasma probes are utilized to measure plasma properties to compare them to the measured performance. A three-dimensional sweep probe apparatus quantifies the effect of the azimuthal magnetic field gradient on the direction of the thrust vector. The azimuthal magnetic field gradient results in decreased stability during operation. The peak-to-peak discharge current oscillations increase by 31.1%, efficiency decreases by 25.7% and thrust decreases by 3.5% (2.7 mN) due to a 16.6% decrease in the local magnetic field resulting in an extreme gradient condition (0.36 G/°). The sweep probe apparatus observes a 24% decrease in the ion beam current and a 5.8° spatial deviation in the thrust vector for the HET with a 0.36 G/° magnetic field gradient. The study presents a physics-based framework that elucidates the observed patterns in thruster performance caused by variations in plasma characteristics. Through the physics-based performance model proposed in the study, the impact of the azimuthal magnetic field gradient on the electron parameters, such as the electron temperature is established. The impact of the azimuthal magnetic field gradient on HET performance and stability is established in the physics-based model by understanding the impact of such a gradient on the motion of the charged particles by utilizing plasma plume parameters.