ABSTRACT
The dispenser cathode is a type of thermionic cathode that uses an impregnant material deposited into the bulk cathode material that continually dispenses a low work function material to the surface. Dispenser cathodes are used in both vacuum and plasma environments; however, the focus of this entry will be on plasma dispenser cathodes. Discharge cathodes offer advantages over vacuum cathodes for two main reasons: 1) discharge cathodes can operate with a higher partial pressure of contaminant gases such as oxygen, and 2) discharge cathodes achieve longer lifetime as a result of redeposition of the low work function material to the surface via gas phase transport. This entry will discuss cathode materials, geometry, and plasma parameters—and the effects these properties have on cathode performance and lifetime.
