Photocathodes-contemporary state and trends

Abstract The basic physical aspects of photoelectric emission from photocathodes and problems connected with the excitation, transport and escape of photoelectrons into vacuum are discussed. Further, the optical properties of the photoelectric emitter, conditions for an effective photoemission and the influence of electron affinity are mentioned. Some characteristics and physical models are presented for photoelectric emission from different types of photocathodes: the silver-oxygen-caesium photocathode, alkali antimonide photocathodes, negative-electron-affinity photocathodes and transferred-electron photocathodes. The significant features of modern photocathodes for application in various electron tubes are stressed.