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Commissioning the Echo-Seeding Experiment ECHO-7 at NLCTA

Commissioning the Echo-Seeding Experiment ECHO-7 at NLCTA. Stephen Weathersby for the ECHO-7 team. D. Xiang, E. Colby, M. Dunning, S. Gilevich, C. Hast, K. Jobe, D. McCormick, J. Nelson, T.O. Raubenheimer, K. Soong, G. Stupakov, Z. Szalata, D. Walz, S. Weathersby, M. Woodley

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Commissioning the Echo-Seeding Experiment ECHO-7 at NLCTA

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  1. Commissioning the Echo-Seeding Experiment ECHO-7 at NLCTA Stephen Weathersby for the ECHO-7 team D. Xiang, E. Colby, M. Dunning, S. Gilevich, C. Hast, K. Jobe, D. McCormick, J. Nelson, T.O. Raubenheimer, K. Soong, G. Stupakov, Z. Szalata, D. Walz, S. Weathersby, M. Woodley SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA P-L. Pernet Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland August-12-2010

  2. Outline • Introduction • Principle of HGHG FEL • The principle of echo enabled HG (EEHG) • Promises and challenges • Echo-7 at NLCTA • Echo-7 first results • Future plans

  3. Introduction • Relates to electron bunch seeding by lasers for short-wavelength radiation generation • Introduction and preservation (echo effect) of fine longitudinal phase space correlations at high harmonics of a seeding laser • Enhancement of the demonstrated high gain harmonic generation (HGHG) seeding technique • Viable candidate for X-ray FEL seeding

  4. Principle of High Gain Harmonic Generation (HGHG) laser • Energy modulation in the modulator • Energy modulation converted to density modulation

  5. Principles of HGHG FEL • HGHG characteristics • Up-conversion efficiency: characterized by bunching factor • k:wavenumberDE: laser modulation • sE: Intrinsic beam energy spread • multiple stages required for X-ray FEL seeding • high power lasers • Large A means large beam energy spread • High peak current ~nI0 • Practical limit is

  6. The principle of EEHG HGHG seed laser 2 laser 1 • First laser to generate energy modulation in electron beam • First strong chicane to split the phase space • Second laser to imprint certain correlations • Second chicane to convert correlations into density modulation

  7. The principle of EEHG • EEHG characteristics • Up-conversion efficiency for maximum bunching: • Nominal first laser modulation: DE1/sE ~ 3 • Bunching is independent of seed amplitude • Seed amplitude determines and final energy spread • Large seed  smaller , large final energy spread • Numerous small current density modulations

  8. EEHG FEL: promises and challenges • Promises (in theory) • Remarkable up-frequency conversion efficiency allows the generation of soft X-rays from UV seed lasers in a single stage • Peak currents are NOT significantly enhanced, which mitigates the collective effects • Challenges • Control & preservation of the phase space correlations • CSR & ISR in the chicanes • Quantum diffusion in the undulators from ISR • Path length difference for particles with different betatron amplitude • Unwanted x-z coupling from field errors, high order field components

  9. World-wide interest in EEHG • China • J.H. Chen, et al, Operating the SDUV-FEL with the EEHG scheme, Proceedings of FEL09, p410 (2009). • France • C. Evain, et al, Study of high harmonic generation at synchrotron SOLEIL using echo enabling technique, Proceedings of IPAC10, p2308 (2010). • Italy • E. Allaria, et al, Feasibilities for single stage echo-enabled harmonic in FERMI FEL-2, Proceedings of FEL09, p39 (2009). • Switzerland • S. Reiche, et al, Seeding option for the soft x-ray beamline of SWISSFLE, Proceedings of FEL09, p51 (2009). • UK • I. Martin, et al, Short pulse options for the UK’s new light source project, Proceedings of IPAC10, p2266 (2010). • USA • J. Corlett, et al, Design studies for a VUV-Soft x-ray FEL facility at LBNL, Proceedings of IPAC10, p2639 (2010).

  10. ECHO-7 at NLCTA existing New ECHO beam line • Install X2 to boost beam from 60 MeV to 120 MeV • Laser transport • Construction of three undulators, three chicanes • Add new or move existing quadrupoles, correctors, etc. • New power supplies • New diagnostics: OTRs, YAGs, cameras, movers, DAQ

  11. ECHO-7 at NLCTA Upstream view

  12. ECHO-7 at NLCTA • Milestones • 03-2009: First planning meeting • 06-2009: LDRD funded • 08-2009: Undulators ordered • 09-2009: BES Funding arrived / First chicane installed • 12-2009: 120 MeV beam achieved • 02-2010: First undulator installed • 04-2010: 795 nm laser-electron interaction achieved • 05-2010: 1590 nm laser-electron interaction achieved • 05-2010: First harmonic radiation observed • 7-2-2010: First echo signal

  13. ECHO-7 at NLCTA • Milestones • 03-2009: First planning meeting • 06-2009: LDRD funded • 08-2009: Undulators ordered • 09-2009: BES Funding arrived / First chicane installed • 12-2009: 120 MeV beam achieved • 02-2010: First undulator installed • 04-2010: 795 nm laser-electron interaction achieved • 05-2010: 1590 nm laser-electron interaction achieved • 05-2010: First harmonic radiation observed • 7-2-2010: First echo signal

  14. ECHO-7 at NLCTA • Milestones • 03-2009: First planning meeting • 06-2009: LDRD funded • 08-2009: Undulators ordered • 09-2009: BES Funding arrived / First chicane installed • 12-2009: 120 MeV beam achieved • 02-2010: First undulator installed • 04-2010: 795 nm laser-electron interaction achieved • 05-2010: 1590 nm laser-electron interaction achieved • 05-2010: First harmonic radiation observed • 7-2-2010: First echo signal

  15. ECHO-7 at NLCTA • Milestones • 03-2009: First planning meeting • 06-2009: LDRD funded • 08-2009: Undulators ordered • 09-2009: BES Funding arrived / First chicane installed • 12-2009: 120 MeV beam achieved • 02-2010: First undulator installed • 04-2010: 795 nm laser-electron interaction achieved • 05-2010: 1590 nm laser-electron interaction achieved • 05-2010: First harmonic radiation observed • 7-2-2010: First echo signal

  16. ECHO-7 at NLCTA • Milestones-2-2010: First echo signal

  17. ECHO-7 at NLCTA • Milestones • 03-2009: First planning meeting • 06-2009: LDRD funded • 08-2009: Undulators ordered • 09-2009: BES Funding arrived / First chicane installed • 12-2009: 120 MeV beam achieved • 02-2010: First undulator installed • 04-2010: 795 nm laser-electron interaction achieved • 05-2010: 1590 nm laser-electron interaction achieved • 05-2010: First harmonic radiation observed • 7-2-2010: First echo signal

  18. ECHO-7 at NLCTA • Milestones X2X-band Length: 75 cm Operating gradient: 80 MV/mMax gradient: 100 MV/m

  19. ECHO-7 at NLCTA • Milestones • 03-2009: First planning meeting • 06-2009: LDRD funded • 08-2009: Undulators ordered • 09-2009: BES Funding arrived / First chicane installed • 12-2009: 120 MeV beam achieved • 02-2010: First undulator installed • 04-2010: 795 nm laser-electron interaction achieved • 05-2010: 1590 nm laser-electron interaction achieved • 05-2010: First harmonic radiation observed • 7-2-2010: First echo signal

  20. ECHO-7 at NLCTA • Milestones • U1, U2 STI Optronics • U3 LBL with adjustable gap • Pneumatically actuated OTR profile monitors

  21. ECHO-7 at NLCTA • Laser system overview • Laser shorter than Beam

  22. Parameters of ECHO-7 (July 2010)

  23. Spatial overlap Beam on OTR1 Beam on OTR2 OTR1 OTR2 Laser on OTR1 Laser on OTR2 The spatial overlap is achieved by steering the laser to the same position as the electron beam on the OTR screens upstream and downstream of the undulators 107 attenuation

  24. Temporal overlap photodiode • The laser and undulator radiation are reflected out by the OTR screen and detected by a fast photodiode. • Scan delay stage to finely adjust the laser timing until the COTR enhancement is observed. 5 ps 1.5 ps Beam off crest in X1 Beam on crest in X1

  25. Radiator Spectrum • Undulator radiation /OTR with UV window • Transmission grating: 300 lines/mm • Insertablebandpassfilters 395 and 531 nm, 11 nm BW • Glass lens and CCD camera

  26. Wavelength calibration 1590 nm laser on Incoherent undulator radiation (a) 795 nm laser on H2 (b) 395 nm bandpass filter in 531 nm bandpass filter in The radiation spectrum [350, 600] nm can be measured in a single shot

  27. HGHG/EEHG predictions • Difficult to distinguish HGHG from EEHG for this range • Somehow need to kill the 1590 nm HGHG contribution to 530 nm radiation • 795 laser does not have harmonic content at 530 nm

  28. Experimental strategy • Establish the HGHG1590 nm setup • Reduce 1590 modulation strength until HGHG signal disappears @ 530 and 397 nm • Turn on 795 nm interaction and see if 530 nm reappears

  29. First ECHO signal! 1590 nm laser only But attenuated No HGHG (a) 795 nm laser only HGHG signal H2 (b) Both lasers on with no 1590 nm HGHG (c) E-1,5 H2 350 400 450 500 550 600 Radiation wavelength (nm)

  30. Separating EEHG from HGHG • Theory predicts spectra shift differently for HGHG and EEHG in the presence of an energy chirp • HGHG • chirp • EEHG

  31. ECHO signals when beam has an energy chirp 1590 nm seed laser on 1590 nm laser on H3 HGHG (a) H4 795 nm laser on H2 795 nm laser on H2 (b) HGHG Both lasers on H4 H2 H3 HGHG + EEHG E1 E3 E2 350 400 450 500 550 600 Radiation wavelength (nm)

  32. Separating EEHG from HGHG • For a chirp h ~ 33.4 m-1 the HGHG (H) and EEHG (E) simulation shows signals become distinct. (M) are ‘mystery echo peaks’ • Such a chirp is applied by moving X2 phase by ~10 degrees simulation

  33. ECHO signals when beam has an energy chirp Both lasers on H4 H2 H3 E1 E3 E2 350 400 450 500 550 600 (b) simulation

  34. Radiation wavelength vs. beam energy chirp Both lasers on H4 H2 H3 H2 E3 E2

  35. Summary of first phase of Echo-7 • Experimental verification of the EEHG scheme • About one year from inception to execution • Basic physics verified for lower harmonics n < 5 • Phase space correlations are preserved • Energy chirp prediction confirmed • First step towards one stage X-ray FEL seeding • Upgrades and diagnostics will allow further characterization of the radiation and realization of higher harmonics

  36. Future plans at NLCTA: T-Cavity • Use transverse cavity to increase beam slice energy spread Both lasers on H2 H3 After the transverse cavity, beam slice energy spread and transverse emittance both grow A transverse cavity with V=100 kV deflection voltage is able to heat the slice energy spread to 10 keV and the transverse emittance only grows from 8 um to 8.5 um

  37. Future plans at NLCTA: THz radiation • Narrow-band Beatwave THz emission Both lasers on H2 H3 1549 nm 795 nm 10 THz Radiation spectrum with (red) and without (blue) laser modulation Beam current with (red) and without (blue) laser modulation

  38. Near future plans for Echo-7 at NLCTA • 08~09, 2010 • Commission our new gun cathode and drive laser • Redo ECHO-3 to Echo-5 • 10, 2010 • Echo-7 • Beatwave THz radiation generation • Studies of Microbunching instabilities • 3~4, 2011 • Use transverse cavity to increase beam slice energy spread and redo the echo experiments • 5~6, 2011 • ECHO-15 and higher

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