Improved Ion Resistance for III-V Photocathodes in High Current Guns

A fundamental issue with high-average-current photoelectron guns is the generation of stray electrons and ions which can damage the photoemitter. Ion back-bombardment of the photoemitter can alter or damage both the photoemitter and the activation layer, resulting in diminished lifetime and poor photo yield, thereby hampering efficient operation. This project will develop technology to enhance the stability of the activation layer and, to a lesser extent, the electron flux, thereby increasing the resistance to stray electrons and ions. In Phase I, the influence of charged particles, ions, and electrons, with varying background gas compositions, on bi-alkali activated photoemitters will be investigated. The secondary electron yield for the modified layer photoemitters will be quantified. Commercial Applications and other Benefits as described by the awardee Improved ion resistance would enable more robust photocathodes to be used in properly designed accelerator injector guns. The proposed research also should provide a foundation for the development of a cold-cathode photon-based electron source with small energy spread and source size, leading to new markets in scanning electron microscopy and other electron based tools.