Inverse Free Electron Laser and Its Applications On Asian...

Brookhaven Science AssociatesU.S. Department of Energy

Inverse Free Electron Laser and Its Applications

X.J. Wang National Synchrotron Light Source

Brookhaven National LaboratoryUpton, NY 11973, USA

Presented at the Fist Asian Summer School on Laser Plasmas Acceleration and Radiations

August 7-11, 2006 Beijing, China

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Laser Plasma Acceleration and Radiations


OutlineOutlineIntroduction – Laser and accelerator, a marriage in heaven?Inverse Free Electron Lase (IFEL):

1. Basic principle and harmonic IFEL2. Experiments: BNL IFEL, Stella, and UCLA

Applications:1. Coherent radiation: HGHG, ESASE2. 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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Light Source Family TreesLight Source Family TreesThe Laser Family The Accelerator Family

Masers

Lasers

CW Pulsed

High Res.Spectroscopy

CD players

SupermarketScanners

Mod. Res.Spectroscopy

Q-switched

Cutting/Welding

Surgery

Ultrafast

Pump/probe

NonlinearOptics

Linacs Storage Rings

Particle Physics

1st Gen. Synchrotron(parasitic)

2nd Gen. Synchrotron(insertion devices)

3rd Gen. Synchrotron(better insertiondevices)

FELs

Far IR

IR/Visible

UV/VUV

SASEX-ray

HHG

Ultrafast, Coherent, Intense X-Rays MaterialsScience

StructuralBiology

X-ray scattering,diffraction & spect.

E. Rolfing. DOE

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LLINACINAC CCOHERENTOHERENT LLIGHTIGHT SSOURCEOURCE

II--280280

Sand Hill RdSand Hill Rd

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LinacLinac--00L L =6 m=6 m




BCBC--11L L =6 m=6 m BCBC--22

L L =22 m=22 m DLDL--22L L =66 m =66 m

DLDL--11L L =12 m=12 m

undulatorundulatorL L =120 m=120 m

7 MeV7 MeV

150 MeV150 MeV 250 MeV250 MeV 4.54 GeV4.54 GeV

14.35 GeV14.35 GeV

...existing linac...existing linac

newnew

rfrfgungun

2525--1a1a3030--8c8c

2121--1b1b2121--1d1d XX

LinacLinac--XXL L =0.6 m=0.6 m

2121--3b3b2424--6d6d

2 cm2 cm

10 cm10 cm

10 cm10 cm 50 cm50 cm

~120 cm~120 cm

θθ ≈≈ 5.75.7ºº 10 period undulator

Initial laser chirp

Polarizer AnalyzerEO Crystal

Bunch charge Gated spectral signal

Spectrometer

ωl

t t ωs

I

Electron bunch

Co-propagatingLaser pulse

Beam pipe

Width gives bunch lengthWidth gives bunch length

Centroid gives arrival timeCentroid gives arrival time

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Brookhaven Science AssociatesU.S. Department of Energy ANL LEUTL Undulator

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Paradise of the Laser Plasma Acceleratorhttp://fls2006.desy.de/index_eng.html

Paradise of the Laser Plasma Acceleratorhttp://fls2006.desy.de/index_eng.html

Higher gradient Lower cost, compact, and broad applications.Better beam quality smaller system

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ChallengesChallengesModern accelerators (light source in particular) usually operate more than 5000 hours/year with better than 95% reliability

Stability and Reliability

Timing jitter

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Multi-particle Coherent Radiation 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

scale comparable to wavelength.

( ) ( ) ( )[ ] ( )ωωω

ωω

ddIfNNN

ddI

clemultiparti1−+=

( ) ( )2

/ˆ∫∞

∞−

⋅= drrSef crni rωωwhere (Nodvick & Saxon)

N can be large e.g. ~ 1010

n(r)

r

bunch density λ << lbE~ N1/2; I ~ N

λ >> lb; E ~ N; I ~ N2

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Short Electron Bunch GenerationShort Electron Bunch Generation

V = V0sin(ωτ)V = V0sin(ωτ)

RF AcceleratingVoltage

RF AcceleratingRF AcceleratingVoltageVoltage

V = V0sin(ωτ)V = V0sin(ωτ)

RF AcceleratingVoltage

RF AcceleratingRF AcceleratingVoltageVoltage

Δz = R56ΔΕ/ΕΔz = R56ΔΕ/Ε

Path Length-EnergyDependent BeamlinePath LengthPath Length--EnergyEnergyDependent BeamlineDependent Beamline

Δz = R56ΔΕ/ΕΔz = R56ΔΕ/Ε

Path Length-EnergyDependent BeamlinePath LengthPath Length--EnergyEnergyDependent BeamlineDependent Beamline

Short electron bunch can be produced by: direction generation;selection; compression, and the combination

ppL Δ

=Δ 2

1γ

l

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IntroductionIntroduction

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A brief History of IFELA 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 IFEL6. Micro-wave IFEL7. Proposal on Ultra-high harmonic generation by IFEL effect.2000: First experimental demonstration of second generation laser accelerator using IFEL at the BNL ATF - StellaHarmonic IFEL and atto-seocnd electron beam generationAtto-second FEL pulse and Enhanced SASE

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)2

1(2

2

2

KU +=γ

λλ

Resonance Condition

Uz

zU

UUzu

uU

kkc

tztckkmc

KeEmc

Ee

cmTBKxtckK

yzBB

+=

−++=Ψ

Ψ=•

=

=−

=

=

/]))([(

)sin('

][][934.0)sin(

)2cos(

0

0

ϖβ

ϖβγ

βγ

λβγ

β

λπ

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Limitation of IFELLimitation of IFELEnergy gain (modulation)

Diffraction:

Spontaneous loss:

λπ 0

220 ])(1[

wRwhere

Rzww

=

+=

P =cZ0Ie

6Nukuγ

2K 2

( ) ( ) ( )[ ]210

0

2 2/2/32 ζζξπγ JJPPNU −=Δ 2/1

2/2

2

KK+

=ξ

laser peak power Bessel functions undulator parameter

number of undulator periods 8.7x109 W2

2

4γζ

ukkK

=

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FEL IFEL

Physics Resonance energy exchange

Same as FEL

e-beam quality

not so critical

Compression

limitation saturation Diffraction, SRapplications Coherent radiation Photon and e-

beam controlinjector

length 20Lp compact

ρσπ

λε

≤

≤

E

2

2γK

2γK

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e-

35

81.6 MHzNd:YAG

LINAC

LASER

LASERCO

2

x

RF GUN

Accelerator Test Facility

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BNL Inverse Free Electron LaserBNL Inverse Free Electron Laser

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Micro-Bunching by IFELMicro-Bunching by IFEL

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STELLA Demonstrated Staging of Laser Acceleration Process

• Staging process demonstrated for first time during Staged ElectronLaser Acceleration (STELLA) Experiment*- Used inverse free electron laser (IFEL) as laser acceleration mechanism- IFEL buncher (IFEL1) creates femtosecond microbunches- IFEL accelerator (IFEL2) accelerates microbunches

*W. D. Kimura, et al., Phys. Rev. Lett. 86, 4041-4043 (2001).

CO2 LASER BEAM

FOCUSING LENSES

VACUUMPIPE

MIRROR WITHCENTRAL HOLE

MIRROR WITHCENTRAL HOLE

E-BEAM

E-BEAMFOCUSING

LENSES

E-BEAMFOCUSING

LENSES

UNDULATORMAGNETARRAY

DIPOLEMAGNET

SPECTROMETERVIDEO CAMERA

= QUADRUPOLE MAGNET

Buncher(IFEL1)

Accelerator(IFEL2)

ADJUSTABLEOPTICALDELAYSTAGE

UNDULATORMAGNETARRAY

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Stellar First Second Generation Laser Accelerator

Stellar First Second Generation Laser Accelerator

IFELPREBUNCHER

DRIFT & e-BEAMFOCUSING

OPTICS

IFELACCELERATOR

DRIVE LASERBEAM

BEAM SPLITTER

ELECTRONBEAM

~30 MW ~100 MW

TROMBONEDELAY LINE

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Schematic Layout of STELLAII Experiment

CO2 LASER BEAMCONVEX MIRROR

VACUUMPIPE

PARABOLICMIRROR WITH

CENTRAL HOLE

E-BEAM

E-BEAMFOCUSING

LENSES

E-BEAMFOCUSING

LENSES

DIPOLEMAGNET

SPECTROMETERVIDEO CAMERA

BUNCHER(IFEL1)

ACCELERATOR(IFEL2)

CHICANETAPERED

UNDULATORARRAY

VACUUMCHAMBER

LENSWINDOW

(1) W. D. Kimura, et al., Phys. Rev. Lett. 92, 054801 (2004).

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Examples of Experimental Results

E-beam only

80% trapping

14% trapping

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UCLA IFEL Experiment

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Theory of Planar Harmonic IFELTheory of Planar Harmonic IFEL

The pendulum equation of the 1-D was extended to include the third harmonic IFEL interaction

( ) ( ) ( )[ ] ( ) ( ) ( )[ ] ξξφψξξφψγ

γ 333sin3sin 213310112 JJEJJEmceK

dzd

oo −++−+−=

⎟⎟⎠

⎞⎜⎜⎝

⎛−= 2

2

1γγψ N

wo k

dzd

2

2

4γξ

w

L

kKk

=

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IFEL Micro-Buncher ConfigurationIFEL 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

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Preliminary results of simulationPreliminary results of simulation

0.6 0.4 0.2 0 0.2 0.4 0.60.02

0.015

0.01

0.005

0

0.005

0.01

0.015

0.02

γ

ψran

0.0015 0.001 5 .10 4 0 5 .10 4 0.001 0.00150

20

40

60Initial Energy Distribution

f3

int3

0.6 0.4 0.2 0 0.2 0.4 0.60

20

40Initial Phase Distribution

f4

int4

We first consider a undulator now exist at the ATF:λu=3.3 cm, Lu =26.4 cm, beam energy 43 MeV, Ku=1.93P1= 150 MW, and P3 = 50 MW

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0.6 0.4 0.2 0 0.2 0.4 0.60.02

0.015

0.01

0.005

0

0.005

0.01

0.015

0.02

Δγi

ψi

0.015 0.01 0.005 0 0.005 0.01 0.0150

20

40

60Exit Energy Distribution

f

int

0.6 0.4 0.2 0 0.2 0.4 0.60

20

40

60Exit Phase Distribution

ψhist

lower2 upper2

int2

0.6 0.4 0.2 0 0.2 0.4 0.60.01

0.005

0

0.005

0.01

Δγi2

ψi2

0.008 0.006 0.004 0.002 0 0.002 0.004 0.006 0.0080

5

10


E2hist

Eint

0.6 0.4 0.2 0 0.2 0.4 0.60

50


ψhist2

lower2 upper2

ψint2

Fundamental only Third harmonic only

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0.6 0.4 0.2 0 0.2 0.4 0.60.015

0.01

0.005

0

0.005

0.01

0.015

Δγi2

ψi2

0.015 0.01 0.005 0 0.005 0.01 0.0150

10


E2hist

Eint

0.6 0.4 0.2 0 0.2 0.4 0.60

50

100


ψhist2

lower2 upper2

ψint2

0.6 0.4 0.2 0 0.2 0.4 0.60.02

0.01

0

0.01

0.02

Δγi2

ψi2

0.02 0.015 0.01 0.005 0 0.005 0.01 0.015 0.020

50


E2hist

Eint

0.6 0.4 0.2 0 0.2 0.4 0.60

100


ψhist2

lower2 upper2

ψint2

Single-Stage Harmonic IFEL Micro-Buncher

Two-Stage Harmonic IFEL Micro-Buncher

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ApplicationsApplications

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.

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OSCILLATOR

SINGLE PASS FEL

SASE

Dispersionnωω

HGHG

Modulator Radiator

Free Electron Laser Configurations

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.

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log

(pow

er)

undulatorlength zsaturation length ~ 10 Lgain

gain

~ 1

05

low gain exponential gain(high-gain linear regime)

P(z) = Po exp(z/Lgain)

non-linear

Self Amplified Spontaneous Emission SASE

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][][][4][min mLkAI

mradmm

w

n −=Α

πελ

ρρϖϖ

ρρ

/1)/(

/

≈≈Δ

=≤Δ

U

FEL

beamFEL

N

PPEE

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Peak Brightness Enhancement From Undulator Radiation To SASEPeak Brightness Enhancement From Undulator Radiation To SASE#of photonsΩx Ωy Ωz

B = (Ωi- phase space area)

# of photons Nlc

~ 106

Enhancement FactorUndulator SASE

αΝe αΝeNlc

compressed

Δ

ΩxΩy (2πεx) (2πεy)

ΩZ ωω

⋅σ Z

c⎛ ⎝ ⎜

⎞ ⎠ ⎟ = 10 −3 ×10 ps Δω

ω⋅

σ Z

c⎛ ⎝ ⎜

⎞ ⎠ ⎟ = 10 −3 ×100 fs 210

210λ 2( )2

B 1023 1033 1010

Nlc: number of electrons within a coherence length lc

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High Gain Harmonic Generation (HGHG) Principle

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

L.H.Yu, Phy. Rev. A, (1991).

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The Success of the Single-Pass High-Gain FELs

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High Gain Harmonic Generation FELHigh Gain Harmonic Generation FEL

Dispersion SectionL=0.3 m

Radiator SectionBw=0.47T λw=3.3cm L=2 m

Seed Laser λ=10.6μm Ppk=0.7 MW

Electron Beam Input Parameters: E= 40 MeV εn= 4π mm-mrad dγ/γ=0.043% I = 110A τe= 4 ps

HGHG FEL λ=5.3 μm Ppk=35 MW

Modulator SectionBw=0.16T λw=8cm L=0.76 m

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NSLS SDL Facility

NSLS SDL Facility

Titanium Sapphire LaserTitanium Sapphire Laser

BNL Photoinjector IVBNL Photoinjector IV

Chicane CompressorChicane Compressor10 m NISUS Wiggler 10 m NISUS Wiggler

300 MeV S300 MeV S--Band Linac Band Linac

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Cutting Edge Science at the SDLCutting Edge Science at the SDL

SASE @ 210 nm

XUV Photochemistry

-1 0 1

-1

0

1

Y-P

ositi

on [m

m]

X-Position [mm]

Elec

tric F

ield

(kV/cm

)

-80

-60

-40

-20

0

20

40

60

80

High Intensity THz

High Brightness Beams

0.23 nm FWHMSASE x105

Wavelength (nm)

HGHG

HGHG FEL @ 266 nm

PRL

PRL

Beam Dynamics

PRSTAB

100 μJ/pulse

LCLS Laser Dazzler Exp-20 -10 0 10 200

0.2

0.4

0.6

0.8

1

Time (ps)

BlueUVIR

80fs Superradiance

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Average output: 100 μJ, 10% fluctuation

266nm HGHG Power vs. Distance in NISUS

0 2 4 6 8 10

100

102

Wiggler Length (m)

Puls

e En

ergy

(μJ

)

(a) 1.8 MW(b) 30 MWTDA

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262 264 266 268 2700

0.2

0.4

0.6

0.8

1

Wavelength (nm)

Ene

rgy

(mJ

(% b

w)-1)

SASE × 105

HGHG

0.23 nm FWHM

x

262 264 266 268 2700

0.2

0.4

0.6

0.8

1

Wavelength (nm)

Ene

rgy

(mJ

(% b

w)-1) SASE × 4

HGHGx

Spectrum of HGHG and SASE at 266 nm

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Ultra-Violet FEL Operation: 200 nm SASEUltra-Violet FEL Operation: 200 nm SASE

185 190 195 2002000

3000

4000

5000

6000

7000

Wavelenght (nm)

Inte

nsity

(a.u

.)

194 196 198 200 202 204

1

2

3

4

5

6 x 104

Wavelength (nm)

Inte

nsity

(a.u

.)

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Brookhaven Science AssociatesU.S. Department of Energy J. Galayda of SLAC

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Histogram of electron longitudinal density

fs

Arb. units σ=55 asfs

Arb. units

2 4 6 8 10

-0.4

-0.2

0.2

0.4

2 4 6 8 10

-0.4

-0.2

0.2

0.4

fs fs

Longitudinal phase space at the exit of the undulator. Modulation amplitude = 40 σe

Longitudinal phase space at the End Station

Simulations (GINGER was used)

cut out with masks

δEin

MeV

δEin

MeV

Estimate: δE=0.6 MeV for P=10 MW, K=1.28, M=55Atto-second Electron Beam Production

In Collaboration with Zolotorev and Zholents

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Peak current, A

σ=140 as

Peak current, A

a)

b)

time, fs

Results for the ATF beam

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Energy modulation in the wiggler at 2 - 4 GeV

Enhanced Self Amplified Spontaneous Emission (ESASE)

Only one optical cycle is shown

Required:

•Laser peak power ~ few GW

•Wiggler with 10 – 20 periods

Assumed:

•Electron energy spread ~ 1.2 MeV

ChicaneLaser Wiggler Linac e-beam

x-rays

Linac Undulator

Master source Near IR pump

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Acceleration to 14.35 GeV and bunching at the laser wavelength

acceleration bunching

Only one optical cycle is shown Pea

k cu

rren

tz /λL

Pea

k cu

rren

t

Ene

rgy

spre

ad

Peak current and energy distribution within one micro-bunch

Bz L 2/λ=Δ

50 fs laser pulseλL= 2 microns

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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), P0~200 GW

70 as( ) xGx Mzz λˆ8Ln2/ +Δ≤Δ

• Each spike is nearly temporary coherent and Fourier transform limited.• Carrier phase for an x-ray wave is random from spike to spike.

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First Experimental Observation of ESASEFirst Experimental Observation of ESASE

195 200 205 2100

0.2

0.4

0.6

0.8

1

Wavelenght (nm)

Nor

mal

ized

Inte

nsity

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National SynchrotronLight Source

Advanced Photon Source

Stanford SynchrotronRadiation Laboratory

Advanced Light Source

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S.Khan of Bessy, FLS2006

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laser wiggler

bendmagnet

mirrorbeamline x-rays

wigglerelectron bunch inthe bend magnet

electronbunch

femtosecondlaser pulse

λW

electronbeam orbit

fs pulse

fs pulse

“dark”pulse

Selection of fs x-ray pulses (femto-slicing)

selection of fs-xrays

A. Zholents, M. Zolotorev, Phys. Rev. Lett. 76, 912, (1996).

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1) by coordinate: x( ),2) by angle: x’( ), 3) by time-off-flight: t( ), 4) by spectra: ω( ) 1)

Selection options:

3) time-off-flight selection

-δ

+δ

4) spectral selection works only for undulator source Mn

1≈

Δωω

harmonic number

number of undulator

i d

Width of the spectral peak of the undulatorradiation

1) H Padmore private discussion

Selection of fs x-ray pulses (2)

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-1200-1000 -800 -600 -400 -200 0 20060

80

100

120

140

160

180

delay (fs)

coun

ts

-1200-1000 -800 -600 -400 -200 0 200

100

150

200

250

coun

ts

-1500 -1000 -500 0 500 1000 1500

2000

2500

coun

ts

0

.2

.4

.6

.8

1.0

x/σ x

time (fs)

Electron Density Distribution

+3σx to +8σx

+4σx to +8σx

Fitted with amplitude of modulation = 6.4 MeVΔ

Laser correlation with visible synchrotron pulse (2)1

R.W.Schoenlein et. al , Science, March 24, 2000

-3σx to +3σx

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1.2

1.0

0.8

0.6

-0.4 -0.2 0.0 0.2 0.4 1086420

1.02

1.00

0.98

0.96

0.94

-6 -4 -2 0 2 4 6

Time (ps)

1.00.80.60.40.20.0

Frequency (THz)

AE=2 AE=4 AE=8

Am

plitude (arb. units)Rel

ativ

e ch

arge

den

sity

a) b)

c) d)

Holy Bunches1/24 ring after slicing

3/4 ring after slicing

Calculated distributions for ALS with nominal and twice nominal momentum compaction.

Holes spread due to time of flight disperson(i.e. momentum compaction)

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Slicing CSR signals

Raw bolometer signal shows a signal synchronous with the laser repetition rate.

1 msec laser rep rate

long slice short sliceThe 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.

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Brookhaven Science AssociatesU.S. Department of Energy http://fls2006.desy.de/index_eng.html

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Generation of attosecond pulses based on SASE FEL: slicing method (Proposal B)

Monochromator: δλ/λ~10-4

Saldin, Schneidmiller, Yurkov, Optics, Com., 237,(2004)

x-rays

UndulatorWigglerLinac

e-beam

%1.02

0

>=Δ

ωδω

EE

~300 asec, ~5 μJ

Selection of attosecondpulse with contrast > 1:1 requires ΔE=40 MeV and laser: 5-fs, 4-mJ

Attosecond x-ray pulse

ω0

ω0+δω

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Laser HeaterLaser Heater

2 cm2 cm

10 cm10 cm

10 cm10 cm 50 cm50 cm

~120 cm~120 cm

θθ ≈≈ 5.75.7ºº

• 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)

10 period undulator

800 nm laser pulse800 nm laser pulse

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Transient Time Method of Optical Stochastic Cooling

. ..radiation pulse amplifier

energy gain/loss

undulator undulator

bypass.

~1 μm

transverse kick

( )

EExxx c Δ

−=−=Δ ηββ

energy kick

A pick-up and a kicker should be installed in a position with a nonzerodispersion function for a simultaneous cooling of energy and transverse coordinates (similar to the Palmer’s method of the momentum cooling).

after kickEEx Δ

=Δ η

before kick

⎟⎠⎞

⎜⎝⎛ zE δ

λπδ 2sin~

δz is particle delay

Mikhalichenko, Zolotorevand Zholents (1993-94)

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Summary and OutlookSummary and OutlookIFEL 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.

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AcknowledgementAcknowledgement

BNL NSLS and ATF colleagueLBL: Zolotorev, Zholents, John ByrdSTI:W. D. KimuraUCLA: D. Cine, C. Pellegrini and P.MusumeciMany other whose work are cited here

Thank you!

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Inverse Free Electron Laser and Its Applications On Asian...

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