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Thomas Jefferson National Accelerator Facility

Thomas Jefferson National Accelerator Facility

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Thomas Jefferson National Accelerator Facility

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  1. Thomas Jefferson National Accelerator Facility Outline of the proposed JLAMP VUV/soft X-ray FEL and the challenges for the photon beamlines and optics J. Michael Klopf Jefferson Lab - Free Electron Laser Division Workshop on Future Light Sources SLAC National Accelerator Laboratory March 1-5, 2010

  2. Thomas Jefferson National Accelerator Facility Outline • Layout and parameters of the existing IR and UV FEL at JLab • Proposed machine design and parameters for the JLAMP VUV/soft X-ray FEL • Requirements on the photon beamlines and optics for the users and for FEL R&D • Challenges for the optical beamline design • damage threshold due to extremely high peak and average brightness • trade-offs between the pulsewidth and bandwidth of the photon pulses • need for and requirements on the monochromator systems • separation and delay control for coaxial high energy and low energy photon sources (e.g. pump-probe experiments) • Preliminary conceptual beamline design • Questions and comments

  3. Thomas Jefferson National Accelerator Facility Jefferson Lab Jefferson Lab Newport News, VA

  4. Thomas Jefferson National Accelerator Facility Existing Jefferson Lab FEL and THz Source IR FEL UV FEL • 150 MeV, 135 pC, 75 MHz ERL driving IR or UV FEL oscillator • IR: 950 nm – 7 mm • UV: 4 eV (fundamental) • 12 eV (3rd harmonic) • high power THz (CSR) collected from final bunching chicane dipole • primarily an ONR • development project • limited user ops DC Gun THz (CSR) IR Wiggler SRF Linac Bunching Chicane UV Transport Line • very high average power • 14 kW IR FEL • 100 W (40 W lab) THz • ultrashort pulses • (100 fs FWHM) Dump

  5. Thomas Jefferson National Accelerator Facility Proposed JLAMP VUV/soft X-ray FEL • Planned design to Operates from 7 eV table-top laser energy to 500 eV with harmonics • 3 to 6 orders greater average brightness than FLASH • Scientific case focused on DOE-BES Grand Challenges from world-class committee • materials science • ARPES (angle resolved photoelectron spectroscopy) • AMO (Atomic, Molecular, Optical Science) • imaging • Secondary goals address BES R&D priorities (injector, srf, collective effects, seed lasers) for next generation hard X-ray photon facility • < $100M and fast schedule since it builds on existing FEL infrastructure

  6. Thomas Jefferson National Accelerator Facility JLAMP in the Light Source Landscape LCLS FLASH Ultimate LS JLAMP JLAMP JLAMP harmonics JLAMP harmonics LCLS FLASH JLAMPdelivers important parameter space un-addressed in hard X-ray proposals, with chemical selectivity to measure atomic structure at the nano-scale, measurement of dynamics on the femto to attosecond timescale of electron motion, and imaging

  7. Thomas Jefferson National Accelerator Facility Proposed JLAMP Upgrade Concept Upgrade three cryomodules to new C100 design with >100 MeV/module Add two recirculations up in energy and two down in energy recovery Maintain IR/UV FEL capabilities

  8. Thomas Jefferson National Accelerator Facility Proposed JLAMP Upgrade Concept • 600 MeV, 2 pass acceleration • 200 pC, 1 mm mrad injector • Up to 4.68 MHz CW repetition rate • Recirculation and energy recovery • 10 nm fundamental output, 10 nm/N harmonic • 50 fs-1000 fs near transform-limited pulses • Baseline: seeded amplifier operation using HHG • HGHG amplifier + oscillator capability • THz Wiggler for synchronized pump/probe

  9. Thomas Jefferson National Accelerator Facility Technical Specs for JLAMP and other Light Sources Items in blue are estimates not from official project sources Items in italics are measured on operational facilities

  10. Thomas Jefferson National Accelerator Facility Competing Light Source Requirements • Some users want ultrashort pulses (time resolved) • Some users want minimum bandwidth (spectroscopy) • Some experiments require high repetition rate (pump-probe, spectroscopy) • Some experiments require low repetition rate or single-shot (extreme conditions, phase changes, microscopy, holography) • Some users want what they cannot have (DE Dt < ħ/2) • Also want to test scalability/feasibility for multipass ERL driven FEL • Need to provide large range of achievable FEL parameters

  11. Thomas Jefferson National Accelerator Facility Challenges for Photon Beamlines and Optics • Damage threshold • average power (thermal management) • peak power (ablation) • Focusing optics must accommodate variable source point (variable curvature) • Control and delivery of required time-bandwidth product (DE Dt) to the user endstation • Monochromator • must operate over very wide spectral band • must be characterized for all polarizations • double-mono necessary for low photon energy • Must preserve coherence of pulses to endstation • Separation of VUV/X-ray and FIR beams (FLASH design)

  12. Thomas Jefferson National Accelerator Facility Damage Threshold for Beamline Optics Numbers to Watch† 300 eV900 eV energy/pulse: 60 mJ 42 mJ s’: 7.9 mrad 3.5 mrad area: 0.98 mm2 0.2 mm2 fluence: 0.06 mJ/mm2 0.2 mJ/mm2 power density: 61 W/mm2 210 W/mm2 * LN2 cooling may be needed * We have experience with cryo-cooled mirrors which enabled the 14 kW operation of the JLab IR FEL †numbers from WIFEL proposal courtesy of Ruben Reininger (BNL)

  13. Thomas Jefferson National Accelerator Facility Damage Threshold for Beamline Optics Ablation: fluence/pulse damage to Au film from a single pulse of the FLASH FEL (l = 98 nm, 40 fs) Peak power density ~ 100 TW/cm2 Material Threshold Fluence Carbon: 0.6 mJ/mm2 Silicon: 0.3 mJ/mm2 Gold: 0.4 mJ/mm2 *sample threshold also critical* courtesy of Ruben Reininger (BNL) and FLASH

  14. Thomas Jefferson National Accelerator Facility Focusing Optics • The source point moves along the length of the wiggler as a function of e- beam energy and the g wavelength • variable curvature – variable focal length • KB mirror pair – simple, control curvature in each plane separately • Is the wavefront preserved? • critical for minimum pulsewidth • could be important in extreme pressure experiments • Other mirror designs (Pros/Cons) • Toroidal • Ellipsoidal

  15. Thomas Jefferson National Accelerator Facility Control of Bandwidth/Pulsewidth • Need to have control of the bandwidth delivered to endstation (monochromator) • Reducing bandwidth increases pulsewidth (transform limit) • Users need to understand bandwidth pulsewidth constraints • Need to have photon diagnostics to characterize bandwidth and pulsewidth parameters • * Will photon diagnostics be supported??? *

  16. k = l/mm a s’ r s Thomas Jefferson National Accelerator Facility Monochromators for FELs • FEL bandwidth will often be greater than the experimental requirements • Monochromators are the primary means for controlling bandwidth • For high g energy: • s’ and l are small • small k  short pulse • For low g energy: • photon beam needs to be “cleaned” of spontaneous and background emission • double mono can clean beam and preserve pulsewidth RMS source limited resolution: RMS illuminated lines: Each line delays l/c: Diffraction limit: courtesy of Ruben Reininger (BNL)

  17. Thomas Jefferson National Accelerator Facility Double Monochromator Design • G : grating M : mirror • Double mono functions like a prism pair in a mode-locked ultrashort pulse laser • Bandwidth controlled by slit width

  18. Thomas Jefferson National Accelerator Facility JLAMP Conceptual Beamline Design 25 m source point K-B mirror pair diffraction gratings full spectrum beam collimator mirror variable slit focusing mirror sample focus VLSGM narrow spectrum beam endstation

  19. Thomas Jefferson National Accelerator Facility Other Beamline Challenges • Will full coherence be preserved to the sample through all of the beamline optics? • JLAMP to also include FIR undulator downstream of VUV/soft X­ray wiggler (pump-probe studies) • coaxial beams to be separated using a mirror with a hole to pass low divergence high energy beam and reflect low energy FIR beam (FLASH) • FIR and X-ray pulse delay scheme at JLAMP to utilize e- bunch “pairs” (FIR pulses lead X-ray pulses) and FIR delay line (unlike FLASH) • WHAT HAVE I MISSED???

  20. Thomas Jefferson National Accelerator Facility Conclusions • FELs can enable time-resolved measurements on a femtosecond or better time scale combined with X-ray measurement techniques • The laws of Physics still hold: DE Dt < ħ/2 • Monochromators will need to operate over a very wide spectral range, and must provide a range of spectral bandwidth • Double monochromator is likely necessary for low g energy to “clean” the beam and preserve the pulsewidth • Average and peak power density must be kept well below damage threshold for beamline optics…and sample!!! (gas attenuator) • Will photon diagnostics be supported??? • WHAT HAVE I MISSED???

  21. Thomas Jefferson National Accelerator Facility Acknowledgements Ruben Reininger (BNL) Peter Johnson (BNL) Hongbo Yang (BNL) Jonathan Rameau (BNL) Michael Gensch (FLASH/DESY) Kevin Morris (CAMD) FEL Team (JLab) This work supported by the Office of Naval Research, the Joint Technology Office, the Commonwealth of Virginia, the Air Force Research Laboratory, The US Army Night Vision Lab, and by DOE under contract DE-AC05-060R23177.

  22. The Jefferson Lab FEL Team April 24, 2009 This work supported by the Office of Naval Research, the Joint Technology Office, the Commonwealth of Virginia, the DOE Air Force Research Laboratory, The US Army Night Vision Lab, and by DOE under contract DE-AC05-060R23177.