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Other Keywords |
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| TUPB29 |
Experimental Optimization of the Cathode Laser Temporal Profile
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laser, emittance, simulation, electron |
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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| TUPC02 |
Photo Injector Cathode Laser Beam Intensity and Pointing Position Diagnostics at PITZ
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laser, diagnostics, monitoring, electron |
147 |
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- Ye. Ivanisenko, G. Asova, J. W. Bähr, S. A. Korepanov, M. Krasilnikov, B. Petrosyan, F. Stephan
DESY Zeuthen, Zeuthen
- O. Kalekin
Erlangen University, Erlangen
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A photo cathode laser with unique parameters is used at the Photo Injector Test facility at DESY in Zeuthen, PITZ. It is cabable of producing laser pulse trains consisting of up to 800 pulses with a repetition rate of 1 MHz where each laser pulse has a flat-top temporal profile. The knowledge of the laser stability is very important for the emittance measurements procedure. Therefore, a system for monitoring the laser beam intensity and pointing position stability was created at PITZ. It is capable of measuring the laser spot position and pulse intensity for each of the laser pulses in the train using a quadrant diode and a photomultiplier tube, respectively. Taking into account the laser beam spot transverse intensity distribution measured by a CCD camera allows to study the position of the laser spot on the photo cathode with a resolution of 8.3 um. Laser intensity measurements can be done for a wide dynamical range of intensities due to the tunable photo multiplier tube gain. The first experiments with the new system show very small laser spot position jitter on the cathode surface of about 20 um and laser intensity fluctuations of about 14 %.
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