Activation Layer Stabilization of High Polarization Photocathodes in Sub-Optimal RF Gun Environments

It is likely that next generation electron sources for future accelerators will initially utilize a direct current gun based injector with a semiconductor photocathode for electron production. The goal of this project is to create a recipe or series of recipes that will immunize a photocathode against the background gasses likely to be found under operation in a generic RF gun, thus reducing or eliminating the need to restrict operation to vacuum environments. The protected/immunized photocathode will retain sufficient quantum yield to satisfy charge requirements and be capable of high polarization electron emission. The process by which such an emitter can be produced and introduced into an RF gun capable of hosting and maintaining these high polarization photocathodes will be generated. The Phase II work will include optimization of the current activation recipe for high polarization photo emitters, quantification of the reactivity of the stabilized surface to other gasses, determination of the effects of the stabilized surface on electron-spin polarization, characterization of the stabilized surface using synchrotron light-source photo emission ,and testing of a-Si emitter layers as a means to achieve even greater immunity. Commercial Applications and other Benefits as described by the awardee: The improved environmental immunity as defined by this work will allow these more robust photocathodes to be used in appropriately designed accelerator injector RF guns. Better immunized photo emitters can also have applications in other low emittance sources. Longer lived photo emitters are desirable to manufacturers of imaging, e.g. night vision, and photomultiplier tubes.