Intrinsic Emittance Reduction of an Electron Beam from Metal Photocathodes
- Paul Scherrer Institute, 5232 Villigen (Switzerland)
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{center_dot}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.
- OSTI ID:
- 21410403
- Journal Information:
- Physical Review Letters, Vol. 104, Issue 23; Other Information: DOI: 10.1103/PhysRevLett.104.234802; (c) 2010 The American Physical Society; ISSN 0031-9007
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BEAM EMITTANCE
BRIGHTNESS
COPPER
ELECTRON BEAMS
ELECTRON SOURCES
FREE ELECTRON LASERS
KINETIC ENERGY
LINEAR ACCELERATORS
PHOTOCATHODES
PHOTONS
QUANTUM EFFICIENCY
WAVELENGTHS
WORK FUNCTIONS
ACCELERATORS
BEAMS
BOSONS
CATHODES
EFFICIENCY
ELECTRODES
ELEMENTARY PARTICLES
ELEMENTS
ENERGY
FUNCTIONS
LASERS
LEPTON BEAMS
MASSLESS PARTICLES
METALS
OPTICAL PROPERTIES
PARTICLE BEAMS
PARTICLE SOURCES
PHYSICAL PROPERTIES
RADIATION SOURCES
TRANSITION ELEMENTS