Robust GaN-Based Photocathodes for High-Current RF Electron Injectors

Photocathodes play a key role in the electron injectors used at DOE accelerator facilities. Metallic photocathodes are very robust, have long lifetimes, and provide the convenience of air transportability. The main disadvantage of these cathodes is their very low quantum efficiency (QE). On the other hand semiconductor cathodes generally have much higher QE but shorter lifetime than metallic cathodes. Hence, there is an immediate need for the development of high QE photocathodes capable of robust operation at high emission currents. This project will investigate the use of GaN-based photocathodes as a candidate technology. In previous work, very-high-emission quantum efficiency values of more than 80% at 120 nm were demonstrated for cesium-activated p-type GaN photocathodes. Phase I will fabricate and characterize robust GaN-based photocathodes for application in high-current RF electron guns. Commercial Applications and other Benefits as described by the awardee Robust photocathodes would enhance the capabilities of photo-injectors, the electron source of choice for future linear accelerators and colliders, energy recovery linear accelerators, fourth generation light sources, injectors for laser-driven plasma wake field accelerators, and high-power free electron lasers. The robust photocathodes also could find use in electron beam lithography and metrology.