X-Ray Free Electron Lasers

X-Ray Free Electron Laserse - SNSNNSLightNSJ.S. WurteleUCB and LBNLDavidson SymposiumPPPLJune 12, 2007X-RayFELs

Two Livingston PlotsParticleacceleratorsLight SourcesPanofskyEU FEL

Evolution of synchrotron radiation sourcesX-Ray FELsGoals:• 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 phasespace• High brightness beam generationand preservation• Wiggler technology

X-ray sources expandJAPAN [SPRING 8]EU XFEL [DESY]CurrentEnergyRepetitionratePeak X-RayPower~3.5kA~13.6GeV~120Hz~8GW!LCLS [SLAC] FEL

Vision for a future LBNL light sourceFEL array at theBevatron siteALSInjectorLinac in tunnel

Vision for a future light source facility at LBNLA HIGH REP-RATE, SEEDED, VUV — SOFT X-RAY FEL ARRAYBeammanipulationandconditioningArray of configurable FELsIndependent control of wavelength, pulseduration, polarizationConfigured with an optical manipulationtechnique; seeded, attosecond, ESASEBeam distribution andindividual beamline tuning~2 GeV CWsuperconducting linacLowemittance,high rep-rateelectron gunLaser systems,timing &synchronization

FEL BASICSLimitsSpread in this term is harmful!

What drives X-ray FELs towards largeenergy electron beams?1. Coherent emission--bunching at X-ray wavelengths2. Limits on our ability to create and propagatehigh brightness electron beams3. Limits on our ability to build short wavelength wigglers

Dephasing from transverse motionJ"undulatorJ "d"dz =+"J #!zJ "ΔE/Ewith conditioning!!z!We are limited by our inability tomake high quality beams• allows relaxed emittance requirement in FEL--but we do not know how to produce requiredconditioning in a practical system (yet)

SASE FEL: amplification of fluctuationsSingle pass synchrotron radiation spectrum (Catravas, et al, @BNL/ATF,)SASE spectrum and temporal shape has spikes--poor longitudinal coherence

0.35Seeded FELENHANCED CAPABILITIES FOR CONTROL OF X-RAY PULSEPulse profile0.4Spectrum0.30Power (GW)0.250.200.150.10SASEPhotons/meV (X10 9 )0.30.20.10.050.00-700 -600 -500 -400 -300 -200 -1000.012381239124012411242Time (fs)Photon Energy (eV)0.60.140.50.12Power (GW)0.40.30.225 fs seedPhotons/meV (X10 9 )0.100.080.060.040.10.0-700 -600 -500 -400 -300 -200 -100Time (fs)0.60.5Seeded FEL close totransform limit0.020.0012383025123912401241Photon Energy (eV)Nomonochromator1242Power (GW)0.40.30.2500 fs seedPhotons/meV (X10 9 )2015100.150.0-700 -600 -500 -400 -300 -200 -100012381239124012411242Time (fs)Photon Energy (eV)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

Phase space manipulationManipulate beam phase space can have many advantages:Enhanced gainSeeding radiation pulse for harmonic cascadesAttosecond pulsesSynchronizationRelax beam quality constraints (conditioning)Lower energy for given wavelengthMany of these ideas are realized by laser interactions withthe electron beam prior to the radiation generation. Someexamples…

Lasers manipulate longitudinal phase spaceduring interaction in wigglerE( t )slice ~ 1 fsLaser pulse e-beam ~ 5 fs~ 100 fsHarmonic cascade seedThis cartoon is realized by manipulation of beam phase space with shortpulse lasers. The idea is to condition and select specific slices ofelectrons to radiate differently (in direction, frequency, intensity, etc.). Forsynchrotron 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)

High Gain Harmonic Generation (HGHG) –seed with a laser pulse and radiate at a harmonicExtends energy reach, lower powere - bunch" 0" 0 nlaser pulsee - beam phase space:Input Output!ModulatorShort wigglerdispersivechicane !RadiatorLonger wigglerEnergy"# phase"Laser modulates e-beamenergyL.-H. Yu et al, Science 289 932-934 (2000)L.-H. Yu et al, Phys. Rev. Let. Vol 91, No. 7, (2003)!"n#Dispersive section introducesbunchingBunched beam radiates strongly atharmonic in a downstream undulator!n"

Cascaded harmonic generation schemeseed laser pulsedisrupted regionmodulatorradiatormodulatorradiatortailheadLow e electron pulseUnperturbed electronss E ~ s E (0)Delay bunch in micro-orbit-bump (~50 mm)Seed laser pulseT bunch >> T MOP MO >> P shotFEL modulatorL W < L SATStrong bunching3rd - 5thharmonicradiator3 - 5th harmonicFEL modulator /low gain amplifierL W < L SAT3rd - 5thharmonicradiator

HHG laser seed--an alternative to harmoniccascadesExample with seed at 30 nm, radiating in the water windowFirst stage amplifies low-power seed with “optical klystron”More initial bunching than could be practically achieved with a single modulatorOutput at 3.8 nm (8 th harmonic)100 kWl =30 nm1 GeV beam500 A1.2 micron emittance75 keV energy spreadModulator30 nm, L=1.8 m300 MW output at 3.8nm (8 th harmonic) froma25 fs FWHM seedModulator30 nm, L=1.8 mRadiator3.8 nm, L=12 mCourtesyH. KapteynOr, X-ray laser seedGullans et al. (2007)

GunBeam manipulationlinacFELsFEL performance is governed by beam brightness:Brightness = # electrons/6D-phase space volumeThis number will NOT get larger---determined by gun physics and emittanceor energy spread can grow through various instabilities

RCD circa ‘89Gullans et al, 2007

Many people within LBNL contribute to new light sourceWalter BarryDan BatesKen BaptisteAli BelkacemJohn ByrdChris CelataChris Coleman-SmithJohn CorlettStefano DeSantisLarry DoolittleRoger FalconeBill FawleyGraham FlemingMiguel FurmanTom GallantMike GreavesSteve GourlayMichael GullensGang HuangZahid HusseinPreston JordanJerry KekosJanos KirzJim KrupnickSlawomir KwiatkowskiSteve LeoneDerun LiSteve LidiaSteve MarksBill McCurdyPat OddoneHoward PadmoreEmanuele PedersoliGregg PennDave PlateIlya PogorelovJi QiangAlex RattiIna ReichelDavid RobinKem RobinsonGlenna RogersRob RyneFernando SannibaleBob SchoenleinAndy SesslerKiran SonnadJohn StaplesChristoph SteierJean-Luc VayMarco VenturiniWill WaldronWeishi WanRussell WellsRussell WilcoxJonathan WurteleSasha ZholentsMike ZismanMax Zolotorev