Internal plasma properties and enhanced performance of 8-centimeter ion thruster discharge

There is a need for a lightweight, low-pow er ion thruster for space scienc e missions. Such an ion thruster is under development. In an effort to bett er understand the discharge performance of this thruster, a version of this thruster with an anode containing electrically isolated electrodes at the cusps was fabricated and tested. Discharge characteristics of this ring cus p ion thruster were measured without ion beam extraction, Discharge current was measured at collection electrodes located at the cusps and at the anod e body itself. Discharge performance and plasma properties were measured as a function of discharge power, which was varied between 20 and 50 W, It wa s found that ion production costs decreased by as much as 20% when the two most-downstream cusp electrodes were allowed to Boat. Floating the electrod es did not give rise to a significant increase in discharge power even thou gh the plasma density increased markedly. The improved performance is attri buted to enhanced electron containment.