Investigating Secondary Electron Yield of Conducting and Insulating Materials

Secondary electron emission (SEE) is thought to play an important role in the initiation of multipactor breakdown on conductors in vacuum electron devices. SEE from insulators is believed to play a key role in flashover on insulating surfaces in vacuum and may depend on the materials electrical stress history. In both cases, SEE strongly depends on any conditioning of the material surface. We present measurements on both conducting and insulating materials of interest in these applications. Measurements are being made in an existing test stand, recently modified to enable measurements on insulators as well as conductors. The system utilizes a hemispherical current collector placed above the sample to collect secondary electrons. Primary electrons are supplied by a < 3 uA, 0 - 1000 eV electron gun. The experimental setup will be described, and recent measurements of SEE of materials under investigation for reduced SEE and improved flashover resistance will be presented.