Experimental investigation of dielectric wall material effects on low-power HEMP thruster

The high efficiency multi-staged plasma (HEMP) thruster, also known as the cusped field thruster, becomes a candidate microthruster of new generation space observation missions for its low complexity and potential long life over a wide range of thrust. Since there is a lack of relevant research of the wall material effects on the HEMP thruster, a low-power HEMP thruster with three different dielectric wall materials is tested to discover the effects on performance and discharge characteristics. A Faraday probe, a retarding potential analyzer, and a Langmuir probe are employed to diagnose the plume, and the plasma behavior differences in ionization and acceleration processes are indicated. The result shows that the secondary electron emission coefficient of the wall material has definite effects under a low mass flow rate, which is similar to the effects on the Hall thrusters, but no distinct difference is found in high flow rate conditions.