Cornell University, Ithaca, New York, USA
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
Beam brightness from modern day photoinjectors is limited by the photocathode. A multifaceted photocathode development program has been undertaken at Cornell University with a goal to develop the ultimate photocathode which has high quantum efficiency, low mean transverse energy, quick response time and a long lifetime. Positive affinity cathodes like CsK2Sb and NaK2Sbhave been grown using different kinds of alkali metal sources (alkali-azide and pure metal) , characterized and tested in the Cornell-ERL photoinjector. Novel layered structures of various III-V semiconductors like GaAs and AlGaAs grown using Molecular Beam Epitaxy and activated to negative electron affinity using Cs and NF3 are also being investigated. Surface and photoemission diagnostics like Auger spectroscopy, LEED, RHEED and the 2D-electron energy analyzers have been connected in vacuum to the photocathode growth and preparation chambers to fully characterize the surface and emission properties of the materials grown. A Monte Carlo based simulation has also been developed to predict photoemission from layered semiconductor structures and help design novel structures to optimize the photoemission properties.
