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LC-ABD P.J. Phillips, W.A. Gillespie (University of Dundee)

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).

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LC-ABD P.J. Phillips, W.A. Gillespie (University of Dundee)

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  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 shapeWakefieldsSynchrotron radiationBeam – Beam interaction

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

  4. Temporal Decoding • 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

  5. Encoding Time Resolution... material response, R(w) • velocity mismatch of Coulomb field and probe laser • frequency mixing efficiency [c (2)(w)] ZnTe GaP Theoretical (but based on some experimental data)

  6. Experimental setup at the VUV-FEL Resulting e-bunches at 450 MeV with 1000 pC in a < 100 fs spike during FEL operation at 32 nm. • 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

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

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

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

  14. Can we get shorter resolution • Lola measurement Actual bunch profile (10 fs resolution) • Coulomb angle 1/g ~ 50 fs for g ~ 1000 • Material • GaP • New material ( Phase matching, c2 considerations) • Gate pulse width ~ 50 fs • Introduce shorter pulse • Spectral interferometry • FROG Measurement • Try these methods on ERLP

  15. Clock to be distributed by fibre lasers through stabilised fibres1 Synchronisation to experiments in future accelerators Synchronisation of RF to Laser pulses is currently to 30 fs over several hundred meters2 Inherently low noise Research into Fibre lasers 1 FEL 2004 J. Kim et al 2 EPAC 2006 A. Winter et al

  16. Fibre Laser

  17. 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 Our Fibre laser interests

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

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