| Paper | Title | Other Keywords | Page | ||
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| THPCH193 | Comparison between H-ion and Heat Cleaning of Cu-metal Cathodes | cathode, gun, DIAMOND, LCLS | 3245 | ||
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Understanding the quantum efficiency (qe) of a metal photocathode in an s-band RF gun is important to limit the drive laser energy requirement and provide the best quality electron beam. Systematic measurements of the qe vs. wavelength for varying surface contamination have been performed on copper samples using x-ray photoelectron spectroscopy (XPS). The sample is first cleaned to the theoretical limit of qe using a 1 keV hydrogen ion beam. The H-ion beam cleans an area approximately 1cm in diameter and has no effect on the surface roughness while removing essentially all contaminants and lowering the work function to 4.3eV. The sample is then exposed to atmospheric contaminants (nitrogen and oxygen) and measured again with XPS to determine the degree of contamination and the effect on the qe. The goal is to determine the best procedure for transferring and installing cathodes in an s-band gun. These results and comparison with a heat cleaned cathode are presented.
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