Primary electric propulsion for future space missions

Performance characteristics of ring-cusp thrusters with xenon propellant

“…A discharge could not be maintained for JD > 12.8 A. When magnet rings numbers 3, 4, and 5 were isolated, no significant change in production cost or discharge voltage occurred. There were also no discharge instabilities.…”

“…As indicated in table VII, most of the discharge current for the high field strength configuration number 5 was collected at ring number 2. This may have contributed to the poor performance and instability of the d~s1gn by loss of energetic electrons directly to the anode without ionizing neutral propellant, and by reducing the effective anode area.…”