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Intrinsic emittance reduction of an electron beam from metal photocathode

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Publication date 2010
Author Hauri Christoph,
Project Low-emittance electron gun development and non-relativistic laser-assisted electron bunch characterization
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Original article (peer-reviewed)

Journal Physical Review Letters
Volume (Issue) 104
Page(s) 234802 - 234805
Title of proceedings Physical Review Letters


Electron beams in modern linear accelerators are now becoming limited in brightness by the intrinsic emittance of the photocathode electron source. Therefore it becomes important for large scale facilities such as free electron lasers to reduce this fundamental limit. In this Letter we present measurements of the intrinsic emittance for different laser wavelength (from 261 to 282 nm) and for different photocathode materials such as Mo, Nb, Al, Cu. Values as low as 0.41±0.03  mm·mrad/mm laser spot size (rms) were measured for a copper photocathode illuminated with a 282 nm laser wavelength. The key element for emittance reduction is a uv laser system which allows adjustment of the laser photon energy to match the effective work function of the cathode material and to emit photoelectrons with a lower initial kinetic energy. The quantum efficiency over the explored wavelength range varies by less than a factor of 3.