1 / 18

Three FEL Designs for the Next Generation Light Source

Three FEL Designs for the Next Generation Light Source. G. Penn , D. Arbelaez , J. Corlett , P.J. Emma, G. Marcus, S . Prestemon , M. Reinsch , R. Wilcox, A. Zholents SLAC 25 September 2013. Next Generation Light Source Soft x-ray FEL facility High repetition rate – 1 MHz

mimir
Download Presentation

Three FEL Designs for the Next Generation Light Source

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Three FEL Designs for the Next Generation Light Source G. Penn, D. Arbelaez, J. Corlett, P.J. Emma, G. Marcus, S. Prestemon, M. Reinsch, R. Wilcox, A. Zholents SLAC 25 September 2013

  2. Next Generation Light Source • Soft x-ray FEL facility • High repetition rate – 1 MHz • CW superconducting Linac to 2.4 GeV • Multiple FEL beamlines using identical bunches • 3 distinct initial FELs for different science needs • nominal bunch: 300 pC, 500 A, 0.6 mm emittance, 150 keV energy spread, b = 10 m • use idealized beam, include resistive wake fields

  3. Beamlines for different purposes 0.2 – 1.2 keV • Self-seeded: high flux, harder x-rays • Long pulses, large pulse energy, better BW than SASE • Highest repetition rate - MHz (no external laser) • Pulse duration and timing set by electron beam • HGHG: stable, transform limited pulses, softer x-rays • Close to transform limit • Adjustable pulse timing, duration and bandwidth • Lower photon energies • 2-Color Chirp-Taper: pump-probe, short pulse • Two short pulses ~2 fs, substantial frequency chirp • independent timing, photon energy, angle 0.1 – 0.72 keV 0.2 – 1 keV

  4. Superconducting undulators for X-rays • Nb3Sn SC undulators, 6 mm magnetic gap • shortest undulator period: lu=20 mm, max K = 5 • allows 0.2 keV up to ~1.5 keV photons in fundamental • HGHG beamline, lu=23 mm, K=6.8 • allows 0.1 keV up to ~1 keV could use shorter undulator periods for dedicated beamlines at ~2.5 keV S. Prestemon et al., PAC 2003, MPPG010

  5. 8.8 m 4.4 m Self-seeded Beamline P SASE stage seeded stage • tuning range 0.2 – 1.2 keV self-seeded • 1.2 keV to 1.5 keV, SASE only • MHz repetition rate • aim for 2% efficiency with resolving power 20,000 mono. 35.2 m 48.4 m 92 m lu = 20 mm both stages 7 meters for monochromator optics

  6. Monochromator selects bandwidth • bandwidth unchanged through seeded stage unless beam has energy chirps typical pulse after monochromator constant bandwidth in seeded stage 80 meV seeded bw ~ 1 eV SASE bw independent peaks, ~ 25 fs width each

  7. Self-seededResults

  8. Self-seeding & coherence • for R=20,000: • ~ 30 fs coherence time at 1 nm wavelength • ~ 130 fs coherence time at Carbon edge (4.5 nm) • pulse duration is defined by electron bunch • 300 fs if no beam manipulations • shorter bunch “core” will not hurt beam brightness • reduces total # photons

  9. HGHG Beamline • tuning range 0.1 – 0.72 keV • 2 stages of HGHG with fresh bunch delay • similar to FEL-2 of FERMI@Elettra • input laser 215 – 260 nm • 100 kHz repetition rate • 200 MW peak power (more for short pulses) fresh bunch 4.4 m mod-1 mod-2 rad-1 rad-2 P 41.6 m 6.0 m 64 m lu = 75 mm lu = 50 mm lu = 23 mm

  10. Relies on fresh bunch delay • fresh bunch needed for high photon energies • input laser at 100 fs FWHM almost overlaps second round of HGHG • ~ 50 fs output duration 150 fs delay increased energy spread hurts performance

  11. Results at 720 eV • ideal beam • total harmonic, 126 • 100 fs input laser • 50 fs output pulse • 2.1 × transform limit 75 meV FWHM 103 eV 50 fs FWHM

  12. HGHG pulse properties • Wigner plot • frequency chirp partly explains 2 × transform limit

  13. HGHG for a Short Bunch • for a 50 fs “core”, barely use 20 fs FWHM seed laser • spacing is too tight and output pulse is quite short • output pulse has 250 meV bandwidth, only 4 fs duration current ramp current ramp

  14. 2-Color Chirp-taper beamline 4.4 m mod1 mod2 3 mm • 2 pulses with one electron bunch, from 0.2 keV to 1 keV • 100 kHz repetition rate pulse 1 P pulse 2 P 0.5 mr lu = 23 mm both radiators 48.4 m 48.4 m 123 m 2.5 fs FWHM 5 mm seed: study 2 mm 0.6 fs FWHM if use chirp to compress

  15. Chirped pulse could be compressed chirped output pulse 5 x more compressed after linear dispersion: close to transform limit

  16. Statistical fluctuations • good transverse mode quality, low background • starts from noise so fluctuates shot to shot • varies mostly in pulse energy • timing, photon energy and chirp very stable shot to shot fluctuations, and averaged profile

  17. Evolution of Pulse

  18. Each beamline serves a role Self-seeded • can use full 1 MHz repetition rate • highest brightness and photon energy HGHG • near transform limit • adjustable parameters, stability from seed laser Two-color chirp-taper • pump-probe at 100 kHz • can scan in time delay, photon energy, orientation

More Related