Investigating Secondary Electron Yield of Materials of Interest for High Power Vacuum Electron Devices and High Voltage Vacuum Insulators

Secondary electron emission (SEE) from conductors is thought to play an important role in the initiation of multipactor breakdown in vacuum electron devices. SEE from insulators is believed to play a key role in flashover on insulating surfaces in vacuum. Additionally, the SEE of an insulator may depend on its 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. A second gun with energies up to 50 keV is also available. 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.