The plasma plume from a 200 W Hall Effect Thruster fueled by iodine vapor was analyzed. The plasma source included a laboratory propellant feed system and a laboratory model Hall thruster powered by a breadboard power processing unit. The hollow cathode was fed with xenon. The distribution of iodine ions was measured with an ExB probe, an electrostatic analyzer (ESA), and a combined ESA/ExB probe. The distribution of xenon ions was also measured. Multiply charge species were detected with both iodine and xenon. Significant populations of diatomic iodine ions were also detected. The dimer fraction was found to vary with operating conditions and angular distance from the beam centroid. The greatest populations of high energy dimers were observed at lower discharge current, and at angles of 30-50 degrees from the beam centroid. At one operating condition, the high energy dimer fraction was approximately 20% by mass in this region. Significant dimer fractions could increase thrust to power by useful amounts at the cost of some overall efficiency.
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