Laser Plasma Acceleration and Radiations

Transcription

1 Inverse Free Electron Laser and Its Applications X.J. Wang National Synchrotron Light Source Brookhaven National Laboratory Upton, NY 11973, USA Presented at the Fist Asian Summer School on Laser Plasmas Acceleration and Radiations August 7-11, 2006 Beijing, China

2 Outline Introduction Laser and accelerator, a marriage in heaven? Inverse Free Electron Lase (IFEL): 1. Basic principle and harmonic IFEL 2. Experiments: BNL IFEL, Stella, and UCLA Applications: 1. Coherent radiation: HGHG, ESASE 2. femto- to atto-second e-pulse and photon pulse: atto-s e- beam, atto-s FEL; femto-slicing in storage ring; 3. Others: heating and cooling, HHG Summer and outlook

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4 Light Source Family Trees High Res. Spectroscopy The Laser Family CD players Supermarket Scanners CW Lasers Cutting/Welding Surgery Mod. Res. Spectroscopy Q-switched Pulsed Brookhaven Masers Science Associates Ultrafast, Coherent, Intense X-Rays HHG Nonlinear Optics Pump/probe Ultrafast UV/VUV Far IR Linacs The Accelerator Family SASE X-ray E. Rolfing. DOE X-ray scattering, diffraction & spect. IR/Visible FELs Particle Physics Materials Science Structural Biology 3rd Gen. Synchrotron (better insertion devices) 2nd Gen. Synchrotron (insertion devices) 1st Gen. Synchrotron (parasitic) Storage Rings

5 LINAC COHERENT LIGHT SOURCE I-280 Sand Hill Rd

6 10 cm 50 cm Beam pipe 2 cm rf gun Linac-0 L =6 m 10 cm new new 7 MeV Linac-1 L =9 m 21-1b 1b θ 5.7º 10 Laser period pulse undulator ~120 cm Electron bunch Co-propagating Linac-X L =0.6 m Initial laser chirp Linac-2 L =330 m 21-3b Polarizer Bunch charge...existing linac 21-1d 1d X 24-6d BC-1 DL-1 L =6 m BC-2 L =12 m L =22 m 150 MeV 250 MeV 4.54 GeV ω l EO Crystal Linac-3 L =550 m 25-1a 30-8c Analyzer Spectrometer t t ω s Width gives bunch length I Gated spectral signal DL-2 L =66 m Centroid gives arrival time GeV undulator L =120 m

7 ANL LEUTL Undulator

8 Paradise of the Laser Plasma Accelerator Higher gradient Lower cost, compact, and broad applications. Better beam quality smaller system

9 Challenges Modern accelerators (light source in particular) usually operate more than 5000 hours/year with better than 95% reliability Stability and Reliability Timing jitter

10 Multi-particle Coherent Radiation What are requirements for CR from electrons in a bunch? bunch (or some portion of it) has density variations on length ( ω ) di dω where scale comparable to wavelength. n(r) multiparti f bunch density cle = [ N + N ( N 1) f ( ω )] r iωnˆ / c ( ω ) e S ( r ) = dr 2 r ( ω ) di dω (Nodvick & Saxon) N can be large e.g. ~ λ << l b E~ N 1/2 ; I ~ N λ >> l b ; E ~ N; I ~ N 2

11 Short Electron Bunch Generation Short electron bunch can be produced by: direction generation; selection; compression, and the combination V = V 0 sin(ωτ) RF RF Accelerating Voltage 1 Δl = L γ 2 Δp p Δz = R 56 ΔΕ/Ε Path Length-Energy Dependent Beamline

12 Introduction

13 A brief History of IFEL 1972 R. Palmer first proposed the idea. 1980s Courant and Pelligrini et al at BNL studied IFEL based accelerator. 1990s: 1. BNL ATF experimental demonstration IFEL effect. 2. HGHG based on IFEL effect. 3. LBNL proposed and demonstrated femto-second electron beam slicing using IFEL effect. 4. Micro-bunching by IFEL observed at the BNL ATF. 5. Optical Cooling based on the IFEL 6. Micro-wave IFEL 7. Proposal on Ultra-high harmonic generation by IFEL effect. 2000: First experimental demonstration of second generation laser accelerator using IFEL at the BNL ATF - Stella Harmonic IFEL and atto-seocnd electron beam generation Atto-second FEL pulse and Enhanced SASE

14 ) 2 ( K = γ U + λ λ Resonance Condition U z z U U U z u u U k k c t z t c k k mc K ee mc E e cm T B K x t c k K y z B B + = + + Ψ = Ψ = = = = = / ] ) )( [( ) sin( ' ] [ ] [ ) sin( ) 2 cos( 0 0 ϖ β ϖ β γ β γ λ β γ β λ π

15 Energy gain (modulation) laser peak power Diffraction: Spontaneous loss: P P Limitation of IFEL 2 ( Δγ ) = 32π ξ[ J ( ζ / 2) J ( ζ / 2) ] 2 N U number of undulator periods 0 0 Bessel functions w = w where 1 8.7x10 9 W [1 + ( ) ] R P = cz 0 Ie 6 = z R undulator parameter 2 K / 2 ξ = 2 1+ K / 2 π 0 w λ N u k u γ 2 K 2 ζ = 2 kk 4γ k u 2

16 Physics e-beam quality FEL Resonance energy exchange ε σ E λ 2 π ρ IFEL Same as FEL not so critical Compression K K 2 2 γ γ limitation saturation Diffraction, SR applications Coherent radiation Photon and e- beam control injector length 20L p compact

17 Nd:YAG CO 2 ASER LASER Accelerator Test Facility 81.6 MHz x 35 LINAC e - RF GUN

18 BNL Inverse Free Electron Laser

19 Micro-Bunching by IFEL

20 STELLA Demonstrated Staging of Laser Acceleration Process Staging process demonstrated for first time during Staged Electron Laser Acceleration (STELLA) Experiment* - Used inverse free electron laser (IFEL) as laser acceleration mechanism - IFEL buncher (IFEL1) creates femtosecond microbunches - IFEL accelerator (IFEL2) accelerates microbunches ADJUSTABLE OPTICAL DELAY STAGE DIPOLE MAGNET SPECTROMETER VIDEO CAMERA Accelerator (IFEL2) E-BEAM FOCUSING LENSES MIRROR WITH CENTRAL HOLE Buncher (IFEL1) UNDULATOR MAGNET ARRAY FOCUSING LENSES E-BEAM FOCUSING LENSES CO2 LASER BEAM UNDULATOR MAGNET ARRAY VACUUM PIPE MIRROR WITH CENTRAL HOLE = QUADRUPOLE MAGNET E-BEAM *W. D. Kimura, et al., Phys. Rev. Lett. 86, (2001).

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22 Stellar First Second Generation Laser Accelerator ELECTRON BEAM IFEL PREBUNCHER DRIVE LASER BEAM DRIFT & e-beam FOCUSING OPTICS BEAM SPLITTER TROMBONE DELAY LINE ~30 MW ~100 MW IFEL ACCELERATOR

23 Schematic Layout of STELLAII Experiment DIPOLE MAGNET SPECTROMETER VIDEO CAMERA CONVEX MIRROR VACUUM PIPE E-BEAM FOCUSING LENSES ACCELERATOR (IFEL2) TAPERED UNDULATOR ARRAY CO2 LASER BEAM BUNCHER (IFEL1) CHICANE WINDOW E-BEAM FOCUSING LENSES (1) W. D. Kimura, et al., Phys. Rev. Lett. 92, (2004). LENS E-BEAM VACUUM CHAMBER PARABOLIC MIRROR WITH CENTRAL HOLE

24 Examples of Experimental Results E-beam only 14% trapping 80% trapping

25 UCLA IFEL Experiment

26 dγ ek = dz γmc Theory of Planar Harmonic IFEL The pendulum equation of the 1-D was extended to include the third harmonic IFEL interaction { E ( ψ + φ )[ J ( ξ ) J ( ξ )] + 3E sin( 3ψ + φ )[ J ( 3ξ ) ( 3ξ )]} sin o o J ξ = dψ o dz k k L w 2 K 4γ γ 1 γ 2 = N kw 2 2

27 IFEL Micro-Buncher Configuration We have considered two options for Harmonic IFEL Micro-Buncher: 1. Single stage undulator with both fundamental and third harmonic IFEL simultaneously present. 2. Two stages of undulators, with fundamental IFEL followed by a harmonic IFEL

28 γ f3 f Preliminary results of simulation ψran Initial Energy Distribution int Initial Phase Distribution int4 We first consider a undulator now exist at the ATF: λ u =3.3 cm, L u =26.4 cm, beam energy 43 MeV, K u =1.93 P 1 = 150 MW, and P 3 = 50 MW

29 Δγi f ψhist int2 ψi Exit Energy Distribution Fundamental only lower int Exit Phase Distribution upper2 Δγi2 E2hist ψhist2 Third harmonic only ψi2 Exit Energy Distribution lower2 Eint Exit Phase Distribution upper ψint2

30 Single-Stage Harmonic IFEL Micro-Buncher Δγi E2hist 10 ψhist2 ψi2 Exit Energy Distribution lower2 Eint Exit Phase Distribution upper ψint2 Two-Stage Harmonic IFEL Micro-Buncher Δγi E2hist 50 ψhist2 100 ψi2 Exit Energy Distribution lower2 Eint Exit Phase Distribution upper ψint2

31 Applications High-gain Harmonic Generation (HGHG). Femto- to atto-s pulse generation: 1. atto-s e-pulse. 2. E-SASE. 3. Atto-s FEL pulse. 4. femto-slicing in a storage ring.

32 SASE HGHG ω OSCILLATOR SINGLE PASS FEL Dispersion Modulator Radiator Free Electron Laser Configurations nω Challenges: 1. High-quality mirrors in UV and X-ray range for oscillator. 2. High-quality electron beam and long undulator for single pass FEL.

33 log (power) Self Amplified Spontaneous Emission SASE low gain exponential gain (high-gain linear regime) P(z) = P o exp(z/l gain ) saturation length ~ 10 L gain non-linear gain ~ 10 5 undulator length z

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35 Δ P ( E FEL Δ / ϖ E = / ρ ϖ ρ P ) beam FEL ρ λ N min [ U Α ] = 1/ 4 πε ρ [ I mm n [ ka ] L mrad w [ m ] ]

36 Peak Brightness Enhancement From Undulator Radiation To SASE # of B = Undulator #of photons Ω x Ω y Ω z (Ω i - phase space area) SASE Enhancement Factor αν photons N lc ~ 10 6 e αν e N lc Ω x Ω y (2πε x ) (2πε y ) Ω Z Δω ω σ Z = ps c ( λ 2) 2 Δω ω σ Z = fs c compressed B N lc : number of electrons within a coherence length l c

37 High Gain Harmonic Generation (HGHG) Principle L.H.Yu, Phy. Rev. A, (1991). HGHG has the following advantages: Longitudinally fully coherent Narrower bandwidth; transform limited Larger ratio of output/spontaneous radiation Central wavelength is stable Pulse length is short & controllable (20 fs) Output fluctuations can be reduced

38 The Success of the Single- Pass High-Gain FELs

39 Seed Laser λ=10.6μm P pk =0.7 MW Modulator Section B w =0.16T λ w =8cm L=0.76 m High Gain Harmonic Generation FEL Dispersion Section L=0.3 m Electron Beam Input Parameters: E= 40 MeV ε n = 4π mm-mrad dγ/γ=0.043% I = 110A τ e = 4 ps HGHG FEL λ=5.3 μm P pk =35 MW Radiator Section B w =0.47T λ w =3.3cm L=2 m

40 NSLS SDL Facility 300 MeV S-Band Linac r e m s a L h c S BNL Photoinjector IV l o o m a u R S d n n a n i a s O t s A n o i t 1 a r e l e c c A a m s a l P r e Chicane Compressor U.S. Department of Energy 10 m NISUS Wiggler 10 m NISUS Wiggler t a i d s n io Titanium Sapphire Laser

41 80fs SASE 210 nm Beam Dynamics Cutting Edge Science at the SDL PRL HGHG 0.23 nm FWHM HGHG FEL 266 (nm) nm SASE x10 5 PRSTAB Time (ps) High LCLS Brightness Laser Dazzler Beams Exp Y-Position [mm] μj/pulse High X-Position Intensity [mm] THz PRL Blue UV IR XUV Photochemistry Electric Field (kv/cm)

42 266nm HGHG Power vs. Distance in NISUS Pulse Energy (μj) (a) 1.8 MW (b) 30 MW TDA Wiggler Length (m) Average output: 100 μj, 10% fluctuation

43 Spectrum of HGHG and SASE at 266 nm Energy (mj (% bw) -1 ) Wavelength (nm) SASE x 10 5 HGHG 0.23 nm FWHM 1-1 ) Energy (mj (% bw) SASE x 4 HGHG Wavelength (nm)

44 Intensity (a.u.) Ultra-Violet FEL Operation: 200 nm SASE Wavelenght (nm) Intensity (a.u.) 6 x Wavelength (nm)

45 J. Galayda of SLAC

46 δe in MeV Atto-second Electron Beam Production Estimate: δe=0.6 MeV for P=10 MW, K=1.28, M=55 Simulations (GINGER was used) fs δe in MeV Longitudinal phase space at the exit of the undulator. Modulation amplitude = 40 σ e Histogram of electron longitudinal density In Collaboration with Zolotorev and Zholents Longitudinal phase space at the End Station fs Arb. units cut out with masks Arb. units σ=55 as fs fs

47 Results for the ATF beam Peak current, A Peak current, A time, fs σ=140 as a) b)

48 Enhanced Self Amplified Spontaneous Emission (ESASE) Master source e-beam Laser Linac Near IR pump Wiggler Energy modulation in the wiggler at 2-4 GeV ly one optical cycle is shown Chicane Linac Undulator Required: Laser peak power ~ few GW Wiggler with periods Assumed: x-rays Electron energy spread ~ 1.2 MeV

49 Acceleration to GeV and bunching at the laser wavelength ly one optical cycle is shown Peak current acceleration Peak current Δz = λl / 2B Energy spread bunching z /λ L 50 fs laser pulse λ L = 2 microns Peak current and energy distribution within one micro-bunch

50 SASE in the undulator producing x-rays synchronized to the modulating laser The output x-ray radiation from a single micro-bunch Power at saturation (estimate for bunching~0.5), P 0 ~200 GW Δz 70 as Δz / 2Ln + ( 8) ˆ λx x M G Each spike is nearly temporary coherent and Fourier transform limited. Carrier phase for an x-ray wave is random from spike to spike.

51 First Experimental Observation of ESASE Normalized Intensity Wavelenght (nm)

52 dvanced Light Source Stanford Brookhaven Synchrotron Science Associates Radiation Laboratory Advanced Photon Source National Synchrotron Light Source

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54 S.Khan of Bessy, FLS2006

55 Selection of fs x-ray pulses (femto-slicing) electron bunch laser femtosecond laser pulse λ W wiggler wiggler electron beam orbit bend magnet beamline electron bunch in the bend magnet mirror selection of fs-xrays x-rays A. Zholents, M. Zolotorev, Phys. Rev. Lett. 76, 912, (1996). fs pulse dark pulse fs pulse

56 Selection of fs x-ray pulses (2) Selection options: 3) time-off-flight selection +δ 4) spectral selection works only for undulator source 1) by coordinate: x( ), 2) by angle: x ( ), 3) by time-off-flight: t( ), 4) by spectra: ω( ) 1) -δ Δω ω harmonic number Width of the spectral peak of the undulator radiation 1 n M number of undulator

57 Laser correlation with visible synchrotron pulse (2) 1 x/σ x Electron Density Distribution time (fs) Fitted with amplitude of modulation = 6.4 MeV counts counts counts Δ delay (fs) R.W.Schoenlein et. al, Science, March 24, σ x to +3σ x +3σ x to +8σ x +4σ x to +8σ x

58 Relative charge density a) b) c) d) Time (ps) Holy Bunches Calculated distributions for ALS with nominal and twice Brookhaven Science nominal Associates momentum compaction /24 ring after slicing Frequency (THz) 3/4 ring after slicing 0.8 A E =2 A E =4 A E =8 1.0 Amplitude (arb. units) Holes spread due to time of flight disperson (i.e. momentum compaction)

59 The signal spectra extend up to 2 THz and depend on the initial laser pulse and proximity to the slice. Fine structure in spectra is due to measurement details. Slicing CSR signals 1 msec laser rep rate Raw bolometer signal shows a signal synchronous with the laser repetition rate. long slice short slice

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61 Generation of attosecond pulses based on SASE FEL: slicing method (Proposal B) Linac e-beam Saldin, Schneidmiller, Yurkov, Optics, Com., 237,(2004) Wiggler Attosecond x-ray pulse ~300 asec, ~5 μj Undulator x-rays Monochromator: δλ/λ~10-4 ω 0 +δω ω 0 2ΔE E δω = > 0.1% ω Selection of attosecond pulse with contrast > 1:1 requires ΔE=40 MeV and laser: 5-fs, 4-mJ 0

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63 800 nm laser pulse 10 cm Laser Heater 10 cm 50 cm θ 5.7º ~120 cm 10 period undulator 2 cm Laser-electron interaction in an undulator induces rapid energy modulation (at 800 nm), to be used as effective energy spread before BC1 (3 kev 40 kev rms) Inside a weak chicane for easy laser access, time-coordinate smearing (emittance growth is completely negligible)

64 Transient Time Method of Optical Stochastic Cooling.. bypass undulator radiation pulse amplifier ~1 μm.. undulator energy gain/loss A pick-up and a kicker should be installed in a position with a nonzero dispersion function for a simultaneous cooling of energy and transverse coordinates (similar to the Palmer s method of the momentum cooling). before kick ΔE Δx = η E { after kick Mikhalichenko, Zolotorev and Zholents ( ) transverse kick Δx = x 2π δ E ~ sin δ z λ δz is particle delay ( c) β x β energy kick ΔE = η E

65 Summary and Outlook IFEL is one of the oldest and most matured laser acceleration techniques, It works. The potential of IFEL is only limited by our imaginations. It will be continued to explored for: 1. Injector for other laser plasma accelerator. 2. Femto- to Atto-s e-pulse and photon pulses. 3. Improve the FEL performance. 4. Control and manipulating the charged particle beam.

66 Acknowledgement BNL NSLS and ATF colleague LBL: Zolotorev, Zholents, John Byrd STI:W. D. Kimura UCLA: D. Cine, C. Pellegrini and P.Musumeci Many other whose work are cited here Thank you!