  An interesting phenomenon observed in the near-anode region of a Hall
thruster is that the anode fall changes from positive to negative upon removal
of the dielectric coating, which is produced on the anode surface during the
normal course of Hall thruster operation. The anode fall might affect the
thruster lifetime and acceleration efficiency. The effect of the anode coating
on the anode fall is studied experimentally using both biased and emissive
probes. Measurements of discharge current oscillations indicate that thruster
operation is more stable with the coated anode.
