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OUTLINE

OUTLINE. ON SOME TIMING JITTER ISSUES FOR THE FERMI  FEL PHOTOINJECTOR LASER SYSTEM Presented by M.B.Danailov Laser Lab, Sincrotrone Trieste danailovm@elettra.trieste.it. Current status of the FERMI project (slides provided by Rene Bakker)

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OUTLINE

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  1. OUTLINE ON SOME TIMING JITTER ISSUES FOR THE FERMI  FEL PHOTOINJECTOR LASER SYSTEM Presented by M.B.Danailov Laser Lab, Sincrotrone Trieste danailovm@elettra.trieste.it Current status of the FERMI project (slides provided by Rene Bakker) Photoinjector laser system and related jitter reduction issues ►required parameters ►main concerns ►near future experiments SLAC XFEL Short Bunch Measurement and Timing Workshop

  2. ELETTRA SLAC XFEL Short Bunch Measurement and Timing Workshop

  3. Undulator Building (new) Experimental User Hall (new) 1 GeV Linac (existing) Booster Synchrotron (under construction) Present linac availability: 22 h/day ELETTRA 2-GeV 3rd generation storage-ring (existing) runs presently 3000 h/year, 24 h/day for special studies FERMI@ELETTRA SLAC XFEL Short Bunch Measurement and Timing Workshop

  4. FERMI@ELETTRA • Key features: • Development of a user-facility. • Based on existing 1-GeV S-band linac infrastructure. • Specifications: • Spectral range (2 undulator lines): • 100 – 40 nm  ( 12 – 30 eV): FEL-1 •  40 – 10 nm ( 30 – 124 eV): FEL-2 • Flexible polarization. • Seeded operation (SASE as optional). • Short pulses (sub-ps  < 100 fs RMS). • 50 Hz repetition rate, 1 micro-pulse per macro-pulse. SLAC XFEL Short Bunch Measurement and Timing Workshop

  5. FERMI@ELETTRA • Present status: • Funding granted • Linac serves as injector for ELETTRA • 2005 – 2006: • (available for FERMI : 22 h/day) • Construction of a new full-energy injector (booster) for ELETTRA • Commencement of FEL construction • 2007 ………… • Implementation and use of the linac FEL user-facility SLAC XFEL Short Bunch Measurement and Timing Workshop

  6. Injector new injector accelerator S0 – S7 old injector RF photo-gun accelerator Present Injector by-pass FERMI@ELETTRA SLAC XFEL Short Bunch Measurement and Timing Workshop

  7. bunch compressor 1 bunch compressor 2 new injector S0 S1 – S5 S6 – S7 old injector linac linac linac BC1 BC2 new injector harmonic cavity (new) FERMI@ELETTRA SLAC XFEL Short Bunch Measurement and Timing Workshop

  8. harmonic cavity FEL-1 user stations new rf photo-injector seed linac linac booster accelerator BC2 BC1 seed FEL-2 30 % tunability FERMI@ELETTRA SLAC XFEL Short Bunch Measurement and Timing Workshop

  9. online diagnostics • focused beam • direct unfocussed beam • monochromatized beam FEL synchronized laser spontaneous radiator photo-cathode laser RF P&P lasers Master Oscillator timing diagnostics linac FEL feedback FERMI@ELETTRA SLAC XFEL Short Bunch Measurement and Timing Workshop

  10. FERMI@ELETTRA 2-Stage High Gain Harmonics Generation 250 nm  50 nm  10 nm SLAC XFEL Short Bunch Measurement and Timing Workshop

  11. 20 ms ~ 2.5 ms accelerating field in linac electron pulse e.g., 50 ns (20 MHz) 20 ms ~ 2.5 ms increase of the average brilliance and flux: 40x FERMI@ELETTRA SLAC XFEL Short Bunch Measurement and Timing Workshop

  12. FERMI PHOTOINJECTOR LASER MAIN PARAMETERS Rep rate: 10 (50) Hz Pulse duration: 2-10 ps (FWHM), ideal pulse shape: flat-top Rise-time: 0.5 ps (10-90%) Spatial profile: top-hat, ~ 1mm 1/e2 radius Fundamental Wavelength 780-800 nm UV wavelength (third harmonic) 260-267 nm Pulse energy (for Cu cathode): Compressed IR amplifier output – 6 mJ /10mJ UV after THG crystal- 0.6 mJ/0.75 mJ UV on the photocathode >0.45 mJ /0.5mJ Timing stability with respect to RF : < 0.5/0.3 ps RMS Energy stability : < 4% RMS / <3 %RMS Stability of the beam position on the photocathode : < 3% 1.5%RMS SLAC XFEL Short Bunch Measurement and Timing Workshop

  13. Ampl2 (Multi-pass, 50 Hz) SS THG Stab Pump Laser 2 cr-cor FERMI PHOTOINJECTOR LASERLAYOUT REF Error sig ? Ampl1 (Regen. , 1 KHz) ML Laser PP TS Pump Laser 1 TS: temporal shaping ; PP : pulse picker ; SS – spatial shaping ; Stab – pulse energy stabilization system cr-cor : cross correlator (SFG intensity -> jitter) SLAC XFEL Short Bunch Measurement and Timing Workshop

  14. OSCILLATOR JITTER • CURRENTLY CHARACTERIZED: • 1.Oscillator : • - home made mirror dispersion controlled (MDC) Cr:LiSAF laser • - Ti:S oscillator with prism dispersion control • 2. Phase-locking : Commercial CLX-1100 Timing Stabiliser , based on single band (100 MHz) PL loop , mixer • Performance: <200 fs RMS short term stability in noise protected environment • Increase to few ps in presence of acoustic noise • STRATEGY FOR IMPROVEMENT: • 1.Oscillator: • MDC Ti:S laser • Frequency-doubled Er-doped fiber laser • 2.Phase-locking: • Use of double band-loop (GHz detector working at harmonic of the rep rate) • Digital phase detector based error measurement SLAC XFEL Short Bunch Measurement and Timing Workshop

  15. FERMI BEAM TRANSPORT SYSTEM Low vacuum enclosure ? Relay imaging Grating PSD1 T PSD2 To phase det • Open questions: • Ray tracing of the transport optics (Relay imaging?) • CW pilot beam for fast opt path monitoring • - Low vacuum path between laser hutch and gun Gun SLAC XFEL Short Bunch Measurement and Timing Workshop

  16. SUMMARY • We hope that the stand-by period of FERMI is about to end • Timing and synchronization would be crucial for the system • Near future tasks on the laser side: • ►decision on the femtosecond oscillator type • ► further development of digital phase detector based jitter monitoring • ►study of diode-pumped regenerative amplifier jitter (cross-correlator based jitter measurement) • ► ray tracing of beam transport system • ►layout of overall timing system SLAC XFEL Short Bunch Measurement and Timing Workshop

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