Characterization of the ion beam and thrust vector of a 5-kW hall effect thruster using a hemispherical sweep probe apparatus

Any manufacturing flaw in Hall effect thruster (HET) components may distort plasma characteristics and thruster performance. The High-Power Electric Propulsion Laboratory of the Georgia Institute of Technology developed a hemispherical sweep apparatus to characterize the three-dimensional ion beam current of the plasma plume. The sweep probe apparatus sweeps a Faraday probe in the vertical and horizontal direction at a constant radius of 1 m across the HET plume to measure the three-dimensional ion current density. The sweep probe is utilized to take measurements of the P5 HET operating at 300 V, 7.9 A on krypton propellant under uniform and azimuthally non-uniform magnetic field configurations in vacuum facility with operational pressure of 3.1 × 10− 6 Torr-Kr. In the uniform magnetic field configuration, the measurements show that the plume center is 4° below the thruster center, a feature not captured by the horizontal sweep of the Faraday probe. The ion beam current measured from the three-dimensional sweep probe apparatus exhibited a 0.03% decrease compared to the conventional horizontal scan using the Sweep Probe Apparatus, whereas the divergence angle showed a 4% variation. In the non-uniform magnetic field configuration, 0.36 G/° azimuthal gradient in the channel, the measurements identified a 24% decrease in ion beam current and a 5.8° spatial deviation of the thrust vector. The sweep apparatus enables an improvement in the ion beam current measurement through three-dimensional plume mapping, plume non-uniformity detection, and thrust vector characterization.