Future x-ray Free-electron laser sources

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  • Thank you for the opportunity to speak here at the postech meeting.. I enjoy the opportunity to visit Korea, and interact with my colleagues in KERI on intense lasers and to find out about new developments in your la boratory.
    Today's talk will present an overview of research on advanced accelerator concepts, starting first with the question: why is it important to pursue work on accelerators, and exploring some of the ideas currently under investigation. While part of this talk will be on neutrino factories and muon colliders, which are really tools used by particle physicists (so far, at least), the other ideas are quite general, and are likely to find their first applications in fields other than particle physics.
    Specially important have been Andy Charman, Ryan Lindberg and Gregg Penn.
    Along the way, I hope to show you that the ideas that we have to address in this work are fundamental ones.
  • the famous Livingston curve, where the energy of accelerators is plotted on a log scale—for high energy physics and light sources-- as a function of the date of operation. Careful examination will show that high energy physics has fallen off the curve. The next x-ray sources will not be off the curve, but scale and cost lead to concern for the future.
    First, these machines are, with the exception of the SLC, storage rings.
    Second, there are fewer Hardron machines than there are e-p machines--Hadron machines were already getting big by 1970, but e-p could still built in many places, as they were not yet large. With LEP, and the LC, this of course, is no longer true.
    At each fall off of a technology a new one has come to the rescue. The winning approach for colliders has yet to be found (muons??). For light sources, I believe the scale and cost is low enough and the demand high enough that we will see significant progress over the next couple of years.
    There many ways that advanced accelerators physics are contributing to other fields.
  • It was realized by the designers of early accelerators that synchrotron radiation will put a fundamental limit on the
    Energy obtainable in circular machines. The basic facts—that a clump of particles radiates as Nxsingle particle so long as the
    Clump, or bunch, as is commonly used, is long, was known many in the fourties. It was not until the 60s, however, that people realized that this radiation could be a fundamental tool for exploring matter. This began a 50 year tradition of condensed matter and more recently bio-physicists, benefiting from the hand-me-downs of HEP.
  • Finally, these machines are colliders. That is, two counter moving beams are collided together. In proton machines, such as the tevatron, beams circulate for more orbits than the earth has made around the sun. The physics questions that arose in the design of these machines motivated, and the scientists involved contributed to, our understanding of the long-time stability of dynamical systems.
    As you certainly have felt here in Texas, the large accelerators that have pushed high energy physics
    forward for close to a century are now approaching a scale that is beyond what society may be willing to support.
    At the same time, light sources, which originated as high-energy hand-me downs, are continuing this tradition, with the building of the LCLS X-ray (.17nm) FEL at SLAC, and a similar facility planned in DESY. They too cannot get much bigger!
    Let’s take a took at the next big accelerator that the high-energy community would like to build.
  • charged particles interact with their electromagnetic environment. It is this
    interaction that of course allows us to accelerate them---we couple into the field that they naturally
    will tend to produce--stimulated emission. But, we must beware--beams
    are self-destructive as they interact with their environment.
  • Desy A pulsed beam of atoms and clusters was illuminated with ~100-fs-long FEL pulses at 98 nm wavelength focussed into a small spot (20 μm diameter) and a power density of up to 7*1013W/cm2. Xenon atoms and clusters are chosen because they can be ionized even by single 12.7 eV photons (the ionisation potential of Xe atoms is 12.1 eV). The resulting ions are detected with a time-of-flight (TOF) mass spectrometer.
  • Follow with cascade with comp theory/exp
  • This is the basic idea that drove plasma accelerators for many years, and has been quite challenging
    to deliver on. Plasmas are not not metal. Look at the top structure, carefully machined, polished,
    vacuum baked to reduce outgassing, and, if cared for, will provide years of good service.
    Now what is this plasma? It not so easy to control---no fusion! It is a hot ionized gas, and one
    cannot form it like a piece of metal. Or can one? John Dawson, who originated and pushed these
    ideas along Toshi tajima from UT, understood that by doing things fast, before
    the ions move, or by controlling their motion,
    that some structures in plasmas can be built. BUT they will not lsat. Ions will move at micons/ns,, so dont waste anytime.
    But this story has a good turn--while the cartoon above has not been
    realized, recent experiments by group at LBL (Leemans group), Malka in France and
    a group at RAL have recently seen well formed 100MeV beams of a feww hundred pico coulombs
    emerging from their experiments. I tell you about this. First how do we make ssructures
  • Future x-ray Free-electron laser sources

    1. 1. X-Ray Free Electron Lasers J.S. Wurtele UCB and LBNL N S S N S S N N e - λ w Light Davidson Symposium PPPL June 12, 2007 X-Ray FELs
    2. 2. Two Livingston Plots Particle accelerators Light Sources Panofsky EU FEL
    3. 3. X-Ray FELs Goals: • High average flux • High peak power • Temporal coherence • Spatial coherence • Attosecond pulses • Synchronization • Flexibility • Implications (current technology): Large machines, GeV Energies • Critical Physics • Optical manipulation of phase space • High brightness beam generation and preservation • Wiggler technology Evolution of synchrotron radiation sources
    4. 4. X-ray sources expand LCLS [SLAC] FEL JAPAN [SPRING 8] Current ~3.5kA Energy ~13.6GeV Repetition rate ~120Hz Peak X-Ray Power ~8GW EU XFEL [DESY]
    5. 5. Vision for a future LBNL light source ALSFEL array at the Bevatron site Injector Linac in tunnel
    6. 6. Vision for a future light source facility at LBNLVision for a future light source facility at LBNL A HIGH REP-RATE, SEEDED, VUV — SOFT X-RAY FEL ARRAY Low-emittance, high rep-rate electron gun Array of configurable FELs Independent control of wavelength, pulse duration, polarization Configured with an optical manipulation technique; seeded, attosecond, ESASE Laser systems, timing & synchronization Beam manipulation and conditioning Beam distribution and individual beamline tuning ~2 GeV CW superconducting linac
    7. 7. FEL BASICS N S S N S S N N e - λ ω Λιγητ Spread in this term is harmful! Limits
    8. 8. What drives X-ray FELs towards large energy electron beams? 1. Coherent emission--bunching at X-ray wavelengths 2. Limits on our ability to create and propagate high brightness electron beams 3. Limits on our ability to build short wavelength wigglers
    9. 9. z undulator zz Dephasing from transverse motion • allows relaxed emittance requirement in FEL--but we do not know how to produce required conditioning in a practical system (yet) ∆E/E with conditioning +κJ⊥ dψ dz = 2kw γ −γr γr J⊥ J⊥ J⊥ We are limited by our inability to make high quality beams
    10. 10. SASE FEL: amplification of fluctuations Single pass synchrotron radiation spectrum (Catravas, et al, @BNL/ATF,) SASE spectrum and temporal shape has spikes-- poor longitudinal coherence
    11. 11. Seeded FEL ENHANCED CAPABILITIES FOR CONTROL OF X-RAY PULSE Electron beam is 1.5 GeV, energy spread 100 keV, 250 A current, 0.25 micron emittance; laser seed is 100 kW at 32 nm; undulator period 1 cm SASE 25 fs seed 500 fs seed 0.4 0.3 0.2 0.1 0.0 Photons/meV (X10 9 ) 12421241124012391238 Photon Energy (eV) 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00 Photons/meV (X10 9 ) 12421241124012391238 Photon Energy (eV) 30 25 20 15 10 5 0 Photons/meV (X10 9 ) 12421241124012391238 Photon Energy (eV) Spectrum 0.6 0.5 0.4 0.3 0.2 0.1 0.0 Power (GW) -700 -600 -500 -400 -300 -200 -100 Time (fs) 0.6 0.5 0.4 0.3 0.2 0.1 0.0 Power (GW) -700 -600 -500 -400 -300 -200 -100 Time (fs) 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 Power (GW) -700 -600 -500 -400 -300 -200 -100 Time (fs) Pulse profile Seeded FEL close to transform limit No monochromator
    12. 12. Phase space manipulation Manipulate beam phase space can have many advantages: Enhanced gain Seeding radiation pulse for harmonic cascades Attosecond pulses Synchronization Relax beam quality constraints (conditioning) Lower energy for given wavelength Many of these ideas are realized by laser interactions with the electron beam prior to the radiation generation. Some examples…
    13. 13. slice ~ 1 fs e-beam ~ 100 fs Lasers manipulate longitudinal phase space during interaction in wiggler This cartoon is realized by manipulation of beam phase space with short pulse lasers. The idea is to condition and select specific slices of electrons to radiate differently (in direction, frequency, intensity, etc.). For synchrotron sources this has already been accomplished: Zholents & Zoloterev (1996); Schoenlein, et al, 2000; Khan, Part. Acc. Conf. 2005. For FEL see Zholents et al (2003- 2007) Harmonic cascade seed Laser pulse ~ 5 fs )t(E
    14. 14. Dispersive section introduces bunching High Gain Harmonic Generation (HGHG) – seed with a laser pulse and radiate at a harmonic L.-H. Yu et al, Science 289 932-934 (2000) L.-H. Yu et al, Phys. Rev. Let. Vol 91, No. 7, (2003) dispersive chicane phase Input Output e- beam phase space: Laser modulates e-beam energy Energy −π π Bunched beam radiates strongly at harmonic in a downstream undulator nπ−nπ Modulator Short wiggler laser pulse e- bunch 0λ Radiator Longer wiggler 0λ n Extends energy reach, lower power
    15. 15. Seed laser pulse Tbunch >> TMO PMO >> Pshot FEL modulator LW < LSAT Strong bunching 3rd - 5th harmonic radiator 3 - 5th harmonic FEL modulator / low gain amplifier LW < LSAT 3rd - 5th harmonic radiator Cascaded harmonic generation scheme Delay bunch in micro-orbit-bump (~50 µm) Low ε electron pulse Unperturbed electrons σE ~ σE (0) seed laser pulse tail head radiator radiatormodulatormodulator disrupted region
    16. 16. HHG laser seed--an alternative to harmonic cascadesExample with seed at 30 nm, radiating in the water window First stage amplifies low-power seed with “optical klystron” More initial bunching than could be practically achieved with a single modulator Output at 3.8 nm (8th harmonic) 300 MW output at 3.8 nm (8th harmonic) from a 25 fs FWHM seed 1 GeV beam 500 A 1.2 micron emittance 75 keV energy spread Gullans et al. (2007) Modulator 30 nm, L=1.8 m Modulator 30 nm, L=1.8 m Radiator 3.8 nm, L=12 m 100 kW λ=30 nm Courtesy H. Kapteyn Or, X-ray laser seed
    17. 17. Gun Beam manipulation FELs linac FEL performance is governed by beam brightness: Brightness = # electrons/6D-phase space volume This number will NOT get larger---determined by gun physics and can grow through various instabilities
    18. 18. RCD circa ‘89 Gullans et al, 2007
    19. 19. 19 Conventional Linac Ez : 10 - 200 MV/ m Lint : km's ∆ ~ K l y s t r o n M i c r o w a v e P o w e r S o u r c e W a v e - g u i d e s t r u c t u r e Δ ~ • E • • h ′ω W = e Ez Lint 0 1 0 2 0 3 0 4 0 5 0 6 0 las er p u ls e Electron beam surfing on plasma electric field ( B. Shadwick, UCB/ CBP) Laser driven plasma based linac Ez : 1 0 - 1 0 0 GV/ m Lint : laser dif fract ion lengt h Plasma-based Electron Linac
    20. 20. 10 14 10 15 10 16 10 17 10 18 10 19 10 20 10 21 10 22 10 23 10 24 10 25 10 26 Average Brightness [Ph/(s 0.1% BW mm 2 mrad 2 )] 10 -5 10 -4 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 3 X-Ray Pulse Duration [ps] 2nd Generation Storage Rings 3rd Generation Storage Rings Cornell ERL (6 keV) European XFEL (12 keV) Seeded FEL, 750 fs (1.2 keV) LCLS (8 keV) BESSY FEL (1 keV) FLASH (200 eV) Seeded FEL, 50 fs (1.2 keV) Seeded FEL, 100 as (1.2 keV) Performance comparison PARAMETER SPACE COMPLEMENTS OTHER FACILITIES
    21. 21. Many people within LBNL contribute to new light sourceMany people within LBNL contribute to new light source Walter Barry Dan Bates Ken Baptiste Ali Belkacem John Byrd Chris Celata Chris Coleman-Smith John Corlett Stefano DeSantis Larry Doolittle Roger Falcone Bill Fawley Graham Fleming Miguel Furman Tom Gallant Mike Greaves Steve Gourlay Michael Gullens Gang Huang Zahid Hussein Preston Jordan Jerry Kekos Janos Kirz Jim Krupnick Slawomir Kwiatkowski Steve Leone Derun Li Steve Lidia Steve Marks Bill McCurdy Pat Oddone Howard Padmore Emanuele Pedersoli Gregg Penn Dave Plate Ilya Pogorelov Ji Qiang Alex Ratti Ina Reichel David Robin Kem Robinson Glenna Rogers Rob Ryne Fernando Sannibale Bob Schoenlein Andy Sessler Kiran Sonnad John Staples Christoph Steier Jean-Luc Vay Marco Venturini Will Waldron Weishi Wan Russell Wells Russell Wilcox Jonathan Wurtele Sasha Zholents Mike Zisman Max Zolotorev
    22. 22. Extras
    23. 23. 800 nm spectral broadening and pulse compression e-beam harmonic-cascade FEL one period wiggler tuned for FEL interaction at 800 nm 2 nm light from FEL 2 nm modulator chicane-buncher 1 nm radiator dump end station 1 nm coherent radiation e-beam end station time delay chicane Potential for attosecond x-ray production e-beam Zholentz and Fawley PRL 2004
    24. 24. X-rays from plasma sources Already demonstrated—beams make x-rays More elaborate ideas based on ion channels [Whittum; E157SLAC] Rousse et al, PRL 04 Many groups worldwide are working on this Plasma yield naturally short pulses, but hard to reach FEL intensities with spontaneous emission [N vs N^2]
    25. 25. The Advanced Photoinjector Experiment – APEX*) *) J. Staples, F. Sannibale, S. Virostek, CBP Tech Note-366, October 2006 Beam Dump Coaxial Gun Cavity Current Monitors Solenoid & Trim Coil Packages Laser Port Beam Position Monitor Retractable Cerenkov Monitor Pepper Pot & Faraday Cup Retractable Cerenkov Monitor & Faraday Cup Cathode Mounted on Coaxial Center Conductor Frequency 65 MHz Field 12-25 MV/m RF power at 20MV/m 70 kW Peak wall power density 8 W/cm2 Vacuum 10-11 Torr 200 MHz is also under consideration High repetition rate RF photocathode gun

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