1. SLAC XFEL Short Bunch Measurement and Timing Workshop 1 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 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

2. SLAC XFEL Short Bunch Measurement and Timing Workshop 2 ELETTRA

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

4. SLAC XFEL Short Bunch Measurement and Timing Workshop 4 Key features: –Development of a user-facility. –Based on existing 1-GeV S-band linac infrastructure. Specifications: –Spectral range (2 undulator lines): 1. 100–40nm  (12–30eV): FEL-1 2.  40 –10nm(30–124eV):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. FERMI@ELETTRA

5. SLAC XFEL Short Bunch Measurement and Timing Workshop 5 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 FERMI@ELETTRA

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

7. SLAC XFEL Short Bunch Measurement and Timing Workshop 7 S0 old injector new injector S1 – S5S6 – S7 bunch compressor 2 bunch compressor 1 BC2 linac harmonic cavity (new) BC1 new injector FERMI@ELETTRA

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

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

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

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

12. SLAC XFEL Short Bunch Measurement and Timing Workshop 12 FERMI PHOTOINJECTOR LASER 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 UVon 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 MAIN PARAMETERS

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

14. 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

15. SLAC XFEL Short Bunch Measurement and Timing Workshop 15 FERMI BEAM TRANSPORT SYSTEM To phase det PSD1 Gun 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 Grating T Relay imaging Low vacuum enclosure ? PSD2

16. 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