Performance of cesium telluride photocathodes as an electron source for the Los Alamos FEL
The Los Alamos Advanced FEL was successfully operated with a Cs{sub 2}Te photocathode driven by a frequency quadrupled Nd:YLF laser as the electron source. Lasing was achieved at 5-6 microns. Cs{sub 2}Te photocathodes with quantum efficiencies of 12-18% at 254 nm were fabricated in an ultrahigh-vacuum chamber and transferred under high vacuum to the FEL. 263 mn light from the drive laser was focused to an 8 mm spot on the center of the photocathode. The authors estimated the operational life time of Cs{sub 2}Te photocathodes to be at least 20 times that for K{sub 2}CsSb photocathodes. The measured dark current of 0.3 mA in an electric field of 22-24 MV/m is well within the acceptable level. The maximum amount of charge extracted was observed to be limited by space charge to about 3.5 nC per micropulse. The emittance of the beam was estimated by fitting the data from a quadrupole scan. The authors measured an emittance that is comparable with the emittance measured with a K{sub 2}CsSb photocathode in their system. A pulse length of 9.3 {+-} 2 ps for 1.3 {+-} 0.2 nC electron micropulses and a pulse length of 7.1 {+-} 0.7 ps for the laser pulses were measured with a streak camera. Therefore, the response of the Cs{sub 2}Te photocathode to the laser pulse is sufficiently fast for FEL applications.
- Research Organization:
- Los Alamos National Lab., NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 10180003
- Report Number(s):
- LA-UR-94-2850; CONF-9408146-3; ON: DE94018302; TRN: 94:008362
- Resource Relation:
- Conference: 16. international free electron laser conference,Stanford, CA (United States),21-26 Aug 1994; Other Information: PBD: [1994]
- Country of Publication:
- United States
- Language:
- English
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