Surface charging by UV irradiation at the alumina RF window

Alumina RF windows are used at high-power RF sources, such as klystrons. The breakdown of RF windows takes place due to multipactor and flashover events on the alumina surface. Both multipactor and surface flashover are considered to be related to the primary electron emission sites, such as the peripheral region of the alumina (the triple junction) and defects on the surface. Photoelectrons induced by ultraviolet light (UV) were emulated as primary electrons. The cathodoluminescence spectra during RF operation and the surface potential profile after the RF were measured and investigated.