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Photocathodes for free electron lasers [electronic resource].

Published:
Washington, D.C. : United States. Dept. of Energy, 1994.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Physical Description:
16 pages : digital, PDF file
Additional Creators:
Los Alamos National Laboratory, United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information
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Summary:
Many different photocathodes have been used as electron sources for FELs and other electron accelerator systems. In choosing one, a compromise between lifetime and quantum efficiency have been unavoidable. High quantum efficiency photocathodes such as CsK₂Sb, Cs₃Sb, and cesiated GaAs have short operational lifetimes and require an ultrahigh-vacuum environment. Long lifetime photocathodes such as LaB₆, Cu, and Y have relatively low quantum efficiencies. However, recently, cesium telluride was found to be an exception. Initial results from CERN and now at Los Alamos have shown that Cs₂Te is reasonably rugged with a high quantum efficiency below 270 nm. Further studies were carried out at Los Alamos in determining its performance as an electron source for the Los Alamos Advanced FEL. The Los Alamos Advanced FEL was successfully operated at 5-6 microns with a Cs₂Te photocathode driven by a frequency quadrupled Nd:YLF laser as the electron source. Cs₂Te photocathodes with quantum efficiencies of 12-18% at 254 mn were fabricated in an ultrahigh-vacuum chamber and transferred under high vacuum to the FEL. The authors estimated that the operational lifetime of Cs₂Te photocathodes to be at least 20 times that for K₂CsSb photocathodes. Furthermore, experiments in the fabrication chamber have shown that heating to 150-200°C photocathodes exposed for one hour at 2×10{sup −4} torr of air was sufficient to revive the quantum efficiency from below 1% to about 10%. The electron beam for the FEL extracted from a cesium telluride target was also characterized. The emittance, response time, saturation level and dark current of cesium telluride photocathodes was determined to be sufficient for FEL applications.
Report Numbers:
E 1.99:la-ur--94-2849
E 1.99: conf-9408146--5
conf-9408146--5
la-ur--94-2849
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Note:
Published through SciTech Connect.
09/01/1994.
"la-ur--94-2849"
" conf-9408146--5"
"DE94018305"
16. international free electron laser conference,Stanford, CA (United States),21-26 Aug 1994.
Kong, S.H.; Kinross-Wright, J.; Sheffield, R.L.; Nuguyen, D.C.
Funding Information:
W-7405-ENG-36
View MARC record | catkey: 14110453