1. LC-ABD P.J. Phillips, W.A. Gillespie (University of Dundee) S. P. Jamison (ASTeC, Daresbury Laboratory) A.M. Macleod (University of Abertay) Collaborators G. Berden, A.F.G. van der Meer (FELIX) B. Steffen, E.-A. Knabbe, H. Schlarb, B. Schmidt, P. Schmüser (DESY) Electro-optic characterisation of bunch longitudinal profile

2. Why do we need an ultra-fast electron bunch diagnostic? Machine operation has high influence on beam shape Wakefields Synchrotron radiation Beam – Beam interaction

3. Electro-optic longitudinal bunch profile measurements  ~ E THz Propagating electric field Effective polarisation rotation proportional to Coulomb field Convert bunch Coulomb field into optical intensity variation. Coulomb field encoded into optical probe Decoding: temporal intensity variations in single laser pulse e-bunch

4. - the chirped laser pulse behind the EO crystal is measured by a short laser pulse with a single shot cross correlation technique - approx. 1mJ laser pulse energy necessary Temporal Decoding

5. Encoding Time Resolution... material response, R(  ) ZnTeGaP velocity mismatch of Coulomb field and probe laser frequency mixing efficiency  (2) (  )] Theoretical (but based on some experimental data)

6. Experimental setup at the VUV-FEL the laser system is housed outside the accelerator tunnel including 4 nJ, 15 fs Ti:Sa oscillator 1 mJ, 30 fs Ti:Sa amplifier the laser beam is transported via a 20m vacuum transfer line current setup allows sampling, spectral and temporal decoding currently ZnTe (185µm) and GaP (170µm) crystal mounted Resulting e-bunches at 450 MeV with 1000 pC in a < 100 fs spike during FEL operation at 32 nm.

7. Laser Hutch at FLASH

8. Temporal Decoding

9. Benchmarking EO by LOLA 450 MeV, 1nC ~20% charge in main peak

10. January-February 2007 results... Electro-optic bunch profile Transverse Deflecting Cavity bunch profile (LOLA)

11. probe laser bunch gate laser Time Calibration....

12. The measured retardation Calculated electric field Simulated EO signal / phase retardation Measured LOLA signal Data taken with GaP (175 um)Q=0.84 nC, r = 3.8 mm; LOLA Res 3.2 fs /pix Current data taken at FLASH Simulation by B. Steffen

13. For a fitted Gaussian curve we get a  of 80 fs +/- 8fs rms

14. Can we get shorter resolution Lola measurement Actual bunch profile (10 fs resolution) Coulomb angle 1/  ~ 50 fs for  ~ 1000 Material –GaP –New material ( Phase matching,  2 considerations) Gate pulse width ~ 50 fs –Introduce shorter pulse –Spectral interferometry –FROG Measurement –Try these methods on ERLP

15. Research into Fibre lasers Clock to be distributed by fibre lasers through stabilised fibres 1 Synchronisation to experiments in future accelerators Synchronisation of RF to Laser pulses is currently to 30 fs over several hundred meters 2 Inherently low noise 1 FEL 2004 J. Kim et al 2 EPAC 2006 A. Winter et al

16. Fibre Laser

17. Our Fibre laser interests Fibre system will exist for timing distribution Exploit for robust / reliability distribution of EO monitors Dual function of precision arrival time monitor Requires Transport of Ti:Sapphire (SHG of Fibre laser ?) knowledge to amplified laser system

18. Conclusions Achieved success at FELIX, DESY Measured an Electron Bunch spike at ~ 80 fs (rms) Wish to do measurements at SLAC