1. Experiences at FLASH and plans for SPARC Patrick O’Keeffe WUTA 2008, 8 th -10 th October Title Patrick O’Keeffe WUTA 2008, 8 th -10 th October

2.  Characteristics of FLASH and Optical Laser  Motivations and Scheme for Synchronisation  Measurement of synchronisation by Cross-correlation  Possible experiments at SPARC What I am going to talk about… Patrick O’Keeffe WUTA 2008, 8 th -10 th October

3. Who am I … o HASYLAB/DESY (Coordinator) o Dublin City University o CNRS / LURE Funded by the 5th Framework Programme of the European Commission Presently: Postdoc at CNR/IMIP in group of Lorenzo Avaldi EU RTD project “X-Ray FEL Pump-Probe” Grant No. HPRI-CT-1999-50009 Host (FEL) Synchronisation Measurements Michael Meyer Patrick O’Keeffe WUTA 2008, 8 th -10 th October

4. Wavelength of VUV radiation 15-50 nm, 150  J 250 m Layout at FLASH RF-gun Cs 2 Te - photocathode Nd:YLF pulse laser (2-20 ps; 262 nm)  10 10 electrons (1-3 nC) SASE undulator 6 modules (each 4.5 m) 0 = 27.3 mm; B 0 = 0.497 T Final energy Up to 1 GeV Experimental Hall FLASH SASE FEL Patrick O’Keeffe WUTA 2008, 8 th -10 th October

5. 100  m 20  m/ unfocused 10  m intensity monitor (gas ionization) optical laser 100  m micro focus 20 m ~42 m to undulator Experimental Hall Patrick O’Keeffe WUTA 2008, 8 th -10 th October

6. Time Structure of the FEL Patrick O’Keeffe WUTA 2008, 8 th -10 th October

7. Wavelength: 790 nm... 830 nm Pulse duration: 100-120 fs pulse energy for single laser pulse: ~ 50 µJ (for 800 pulses in macropulse) up to 1 mJ (10 Hz pulse rep. rate) Laser parameters Optical Laser Courtesy: Ingo Will MBI (Berlin) Patrick O’Keeffe WUTA 2008, 8 th -10 th October

8. Motivations for Synchronisation Motivation: Pump-probe experiments Atomic / Molecular Physics (e.g. dynamics /nonlin. processes in VUV/XUV/X-ray) Solid state dynamics (e.g. magnetization dynamics, non-thermal melting) Plasma physics (probing high electron densities) Patrick O’Keeffe WUTA 2008, 8 th -10 th October

9. Difficulties to be surmounted for Synchronisation Classical same source set-up  Photocathode laser, accelerator RF and pump-probe laser independently synchronised with master oscillator and far apart  Thermal drifts  Accuracy of the electronic synchronisation  Phase jitter of the accelerator RF pulses → several 100 fs time jitter Independent sources: Patrick O’Keeffe WUTA 2008, 8 th -10 th October

10. Synchronisation Scheme...100 ms... systematic drifts within the pulse ~100 fs systematic drifts within the pulse ~100 fs changes from macropulse to macropulse ~ 300 fs changes from macropulse to macropulse ~ 300 fs...hours... l ongterm drifts > ps l ongterm drifts > ps Injector laser linac undulator pump - probe laser electron pulse compression Klystron main oscillator experiment Temperature stabilised Cables (300m) 1.3 GHz and 108 MHz Patrick O’Keeffe WUTA 2008, 8 th -10 th October

11. Jitter problem Measurement of relative arrival time between opt. laser pulse and FEL pulse and “sort” data points afterwards to correct jitter Patrick O’Keeffe WUTA 2008, 8 th -10 th October

12. bending magnet synchroscan streak camera  slow feedback goal: drift < ps / h master clock from injector rack   300 m long cables linac FEL Ti:Sa laser 790 nm – 830 nm 150 fs electrons FEL to user opt. laser to user visible synchrotron radiation electrons Cross correlation Hamamatsu C5680 synchroscan res: 2 ps Cost: EUR 150 000 Optical laser + Synchrotron Radiation Courtesy: Stefan Düsterer (Hamburg) Patrick O’Keeffe WUTA 2008, 8 th -10 th October

13. Dipole radiation used for slow feedback Monitoring used to correct for thermal changes in the synchronisation cables Not sufficient resolution for true measure of jitter Patrick O’Keeffe WUTA 2008, 8 th -10 th October

14. Cross Correlation in ATI of rare gases Ar( 1 S 0 ) Ar(IP)15.76 eV h  ir =1.55eV Sidebands (intensity prop. to intensity of IR) h  xuv = 26 eV Patrick O’Keeffe WUTA 2008, 8 th -10 th October

15. Set-up used in the Hamburg Experiments Patrick O’Keeffe WUTA 2008, 8 th -10 th October

16. Transport of the Optical Pulse Patrick O’Keeffe WUTA 2008, 8 th -10 th October

17. First Experiment - 2005 M. Meyer, D. Cubaynes,P. O’Keeffe, H. Luna, P. Yeates, E. T. Kennedy, J. T. Costello, P. Orr, R. Taïeb, A. Maquet, S. Düsterer, P. Radcliffe, H. Redlin, A. Azima, E. Plönjes, and J. Feldhaus PHYSICAL REVIEW A 74, 011401R 2006 Cross correlation: FEL 32.2 nm (50fs – 40  J) Laser 523 nm (12ps – 250  J) Tcross = 12.0 +/- 0.4 ps Sideband Intensity = 2% of Main He line Patrick O’Keeffe WUTA 2008, 8 th -10 th October

18. Second Iteration! Cross correlation: FEL 13.8 and 25.5 nm (15-20 fs – 50  J) Laser 800 nm (120 fs – 20  J) Integrated Intensity of Sidebands = 20 % P. Radcliffe, et al., Appl. Phys. Lett. 90, 131108 (2007). Tcross = 600 +/- 50 fs (FWHM) Jitter = 590 fs (FWHM) 250 fs (r.m.s.) Patrick O’Keeffe WUTA 2008, 8 th -10 th October

19. Single shot cross-correlation in Xe Cross correlation: FEL 13.8 (15-20 fs – 50  J) – 89.9 eV Laser 800 nm (120 fs – 20  J) Comparison of the sideband intensity with theoretical analysis Temporal delay determined with a precision of +/- 50 fs P. Radcliffe, et al., Appl. Phys. Lett. 90, 131108 (2007). Patrick O’Keeffe WUTA 2008, 8 th -10 th October

20. SPARC vs FLASH SPARCFLASH Wavelength15 - 45 nm500 nm Power400  J150  J VisibleEUV Temporal Width2 ps10s fs Visible : temporal structure via autocorrelation Characteristics of SPARC similar to commercial ps YAG Patrick O’Keeffe WUTA 2008, 8 th -10 th October

21. Above Threshold Ionisation with SPARC McIlrath et al. Phys. Rev. A 35 (1987) 4611 10 15 photons/pulse @ 500nm 2 ps focussed to 50  m 10 13 W/cm 2 Patrick O’Keeffe WUTA 2008, 8 th -10 th October

22. IMIP Group experience SPARC Project CNR–IMIP, Poli MI, UniNa,UniPd Science 314(2006)443

23. Seeding of SPARC Two seeding schemes mentioned in TDR produce: 53.2 nm = 23.3 eV 32 nm = 38.7 eV Optically based autocorrelation methods become difficult Pulses on the 10s fs – 100fs scale Could use cross-correlation methods for characterisation of the temporal structure of the FEL Patrick O’Keeffe WUTA 2008, 8 th -10 th October

24. Dynamics of Excited Ionic States State of the art of gas phase pump-probe: Soft X-ray–Driven Femtosecond Molecular Dynamics Murnane and Kapteyn and coworkers: Science 317, 1374 (2007); Photons /pulse HHGSeeded SPARC ~10 6 10 6 - 10 7 Patrick O’Keeffe WUTA 2008, 8 th -10 th October

25. Acknowledgements Members of the “X-Ray FEL Pump-Probe” EU RTD project Michael Meyer Lorenzo Avaldi, Paola Bolognesi, Roberto Flammini Patrick O’Keeffe WUTA 2008, 8 th -10 th October