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| TUPB29 |
Experimental Optimization of the Cathode Laser Temporal Profile
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135 |
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- M. Krasilnikov
DESY, Hamburg
- J. W. Bähr, M. Hänel, F. Stephan
DESY Zeuthen, Zeuthen
- I. Will
MBI, Berlin
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Producing a flat-top temporal intensity profile of the cathode laser pulse is a key issue for the XFEL photo injector. The photo injector test facility at DESY in Zeuthen (PITZ) serves as a test bench for FEL photo injectors. The PITZ cathode laser contains a pulse shaper to produce flat-top temporal pulse profiles. Based on birefringent filters the pulse shaper includes four degrees of freedom to achieve a pulse profile with parameters closer to the required XFEL photo injector specifications (20 ps FWHM, 2 ps rise/fall time). A procedure for experimental temporal laser profile optimization is presented in this paper. The laser profile is measured using a streak camera. The four parameters - pulse length (FWHM), rise and fall time as well as modulation of the flat-top which are obtained from a flat-top fit of the measured profile - are used in the profile evaluation. Utilizing results of beam dynamics simulations for various cathode laser profiles a single value of the goal function – the expected emittance growth due to measured imperfections of the profile - can be obtained. The procedure of the goal function minimization has been implemented and tested at PITZ.
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