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Proposal for optimizing the cathode laser shape for photo injector

This proposal presents a procedure for optimizing the cathode laser shape for a photo injector, using laser pulse shaping techniques. It includes measurements with a streak camera, controlling the temporal profile, and an evaluation of the temporal pulse profile. The goal is to improve the laser profile for better electron beam properties. Further optimization algorithms and parameter adjustments are needed for efficient and accurate results. Feedback control of the cathode laser profile can also be implemented.

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Proposal for optimizing the cathode laser shape for photo injector

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  1. Proposal for optimizing the cathode laser shape for photo injector M. Krasilnikov, DESY Mini - Workshop on Laser Pulse Shaping DESY Zeuthen 30.11-01.12.2006

  2. Outline • Laser pulse shaper at PITZ: • … • Measurements with streak-camera • Controlling the temporal profile • Optimization of the temporal pulse profile: • Goal function for the evaluation of the temporal pulse profile • Setup • Example of laser pulse profile optimization at PITZ • Conclusions M.Krasilnikov, DESY

  3. Laser pulse shaping at PITZ PITZ pulse shaper Streak-camera M.Krasilnikov, DESY

  4. Laser pulse profiles at PITZ which is better? M.Krasilnikov, DESY

  5. Laser pulse shape analyzer: spectrum One possible approach – spectrum analysis… FWHM=20 ps rt=2 ps t, ps M.Krasilnikov, DESY

  6. Laser pulse shape analyzer hmax mu2 mu1 hmin rt2 rt1 %initial guess parameters mu1=0.1; %low threshould level for time windows 0.1->10% mu2=0.2; %low threshould level for time windows 0.2=> 1-0.2->80% hmin=0; hmax=> to be determined from area %max number of iterations MaxIter=50; M.Krasilnikov, DESY

  7. Laser pulse shape analyzer M.Krasilnikov, DESY

  8. Laser pulse shape analyzer Laser Profile Evaluation For instance: FWHM, rt1, rt2, FT-modulation LPE=… (mm mrad) M.Krasilnikov, DESY

  9. Laser Profile Quality Impact of the laser temporal profile imperfections ASTRA simulations M.Krasilnikov, DESY

  10. Laser Profile Quality Combined Goal Function LPE(rt,fwhm) M.Krasilnikov, DESY

  11. Cathode laser imperfections: FT modulation Cathode laser intensity and electron bunch density Emittance growth due to flat-top modulation M.Krasilnikov, DESY

  12. Cathode laser imperfections: FT modulation Microbunching instability gain (courtesy M.Dohlus) Electron bunch density modulation vs. cathode laser intensity modulation 30 M.Krasilnikov, DESY

  13. Setup Streak-camera (Hamamatsu C5680) HPD-TA32 Image server Laser Profile Evaluation Profile Profile Analyzer fwhm, rt1,rt2,mod LPE LPE optimization File (AFS) PITZ pulse shaper M.Krasilnikov, DESY

  14. Pulse shape measurements T1 T2 Rot1 Rot2 M.Krasilnikov, DESY

  15. Optimization* T1 T2 Rot1 Rot2 *no modulation factor has been applied M.Krasilnikov, DESY

  16. Optimization T1 T2 Rot1 Rot2 modulation factor included M.Krasilnikov, DESY

  17. Procedure for evaluation of the temporal laser profile has been suggested. It’s based on theoretical expectations of the electron beam properties in dependence on cathode laser imperfections: (FWHM, rise/fall time, FT-modulation) Since no well-determined algorithm for the laser pulse shaper at PITZ adjustment (T1,T2,Rot1,Rot2) exists, several approaches have been tried: We are looking forward to apply more efficient algorithms (i.e. generic..), but more understanding of adjusting parameters are necessary Such as a procedure can be also applied for the feedback control of the cathode laser profile Conclusions and outlook M.Krasilnikov, DESY

  18. M.Krasilnikov, DESY

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