Robust RF Photocathodes

Existing high quantum efficiency (QE) photocathodes experience very short lifetimes, often only a few hours. Because of the fabrication expense for these cathodes, commercial use is impractical for most applications. Photocathodes with long lifetime are needed to make photoguns cost effective for commercial applications. CCR and the University of Maryland are applying controlled porosity reservoir cathode technology to increase lifetime and provide recovery of contaminated photocathodes. The goal is to extend the lifetime of high QE photocathodes by more than two orders of magnitude. The Phase I program demonstrated that reservoir technology is applicable to photocathodes. Cesiated tungsten cathode lifetime was extended from approximately 100 hours to more than 30,000 hours. The technique was tested and verified for photocathode materials with QE exceeding 1%. The Phase II program will develop fabrication techniques for photocathodes with high QE at production volumes. Because these cathodes cannot be exposed to air, it will be necessary to develop techniques and tooling to handle, transport, and install cathodes at user facilities. The program will include extensive testing to confirm that remotely fabricated photocathodes can be successfully transported, installed, and operated. High power testing will be performed at SLAC National Accelerator Laboratory. Commercial Applications and Other Benefits: This technology would be applicable to high performance accelerators and colliders, as well as light sources for advanced research. Implementation in electron microscopes would provide ultrafast electron microscopy with time resolution on the femto-second time scales.