Application of ultrafast laser techniques in accelerators Yuelin Li Accelerator Systems Division Argonne National Laboratory [email protected]

Application of ultrafast laser techniques in accelerators

Yuelin LiAccelerator Systems DivisionArgonne National [email protected]

2Sector 7 seminar, July 8, 2008

Acknowledgements

ColleaguesSteve Milton, Kwang-Je Kim, Kathy Harkay, John Lewellen, Vadim Sajaev,

Yong-chul Chae, Yin-e Sun (Argonne National Laboratory)

Guest scientists:Baifei Shen (Shanghai Institute of Optics and Fine Mechanics)

Karoly Nemeth, John Bailey


Content Laser and accelerator history Laser applications in accelerators Review of recent laser/accelerators work at the APS

– Electro-optical sampling

– Free-electron laser characterization

– Ultrashort, bright x-ray, Gamma-ray, and positron pulses

– Coherent THz generation

– Laser plasma accelerator simulation

– 3-D Laser pulse shaping for photoinjectors Summary


Lasers and accelerators at birth

Ancient: Let there be light…………………..1917, theory of stimulated

radiation by Einstein1960, flash-lamp pumped

ruby, Dr. Mainman1964, Nobel Prize, Towne,

Basov, and Prokhorov

Ancient: a cave man’s bow……………….1929, Cyclotron, Lawrence1939, Nobel Prize, Lawrence


A map for laser applications in accelerators

Beam generation

Beam Characterizationmonitoring

BeamProcessing treatment

Radiation/particle source generationCharacterization

• Laser/accelerator synchronization• Laser pulse shaping • Plasma wake wave accelerator

• Laser beam cooling/heating• Laser modulation

• Laser beam scattering• Electroptical sampling • Inverse free-electron laser

• Laser beam scattering• Laser beam timing • Laser modulation










Electro-optical sampling and application

To measure the longitudinal beam profile

– Yan et al., PRL 85, 3404 (2000);– Berden et al., PRL 93, 114802 (2004), 300 fs

To measure beam position and transverse beam profile

– R&D at NIU and Spting8 As a timing tag

– SPPS: Cavalieri et al., PRL 94, 114801 (2005), 300 fs To measure THz radiation

– TDS, etc


413

, 2

1Ernnn yx

EllErn 441

3

1027.7~2

)].cos(1[

)],cos(1[

0//

0

p

p

II

II

0: crystal residual or bias birefringence

(001)

z (110)

x

yp

pE

E beam

Laser

P1 P2

e beam

Probe laser

Off line test of Electro-optical sampling (EOS) as electron beam diagnostics


Effect of optical bias

The signal can be linear or nonlinear depends on the relative magnitude of 0 and

The signal can flip sign artificially!

]cos1[ 0pI

Background Raw data Background subtracted

)]cos(1[ 0 pI

.)2()2(

)]cos([cos

02

0

00

pp

p

II

I


Nonlinear response at near-zero-optical bias geometryexperiment results

5x101 5x102 5x103 5x104

-0.4

0.0

0.4

0.8

1.2

0

2

4

6

(b) >0

E (V/m)

I Sig

nal (ar

b. u

nits) (a) <0

False field minimum

Artificial sign flip

Li et al., Appl. Phys. Lett. 88, 251108 (2006)

.)2( 0 psig II


Implications

One has to know 0 to retrieve

– Timing: when it starts?

– Amplitude: what is the maximum?

Or work at larger optical bias

– Combating with big background with smaller signal

It has significant implication for using EOS as timing and profile measurement techniques

5 6 7 8-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

B

C

D

A

I (a.

u.)

t (ps)




– Femto statistic optics using a free electron laser






Free electron lasers

• Grow from noise• Microbunching-

>amplification• Slippage->coherence

buildup• Continuously tunable• X-ray capability


APS free electron laser and

6 Hz, 0.5 ps, 50 J @ 120-530 nmMilton et al., Science 292, 2037 (2001)

laser pulse

Beam splitter

BBO crystal

Cylindricallens

Correlation signalonto spectrometer


What to analyze

0.0

0.3

0.5

0.8

1.0

-600 -400 -200 0 200 400 6005.0

5.5

6.0

6.5

7.0

526 528 530 532 534 5360.0

0.5

1.0

1.5

2.0

2.5

3.0

-600 -400 -200 0 200 400 600

268

267

266

265

264

263 Raw

(fs)

(n

m)

-600 -400 -200 0 200 400 600

268

267

266

265

264

263 Reconstructed

(fs)

Time

Inte

nsi

ty (

a. u

. )

t (fs)

Intensity Phase

Ph

ase

(rad

)

(nm)

-600 -400 -200 0 200 400 600

'"

'"

It

t (fs)

• Retrieve the amplitude and phase• Measure the statistic properties of phase, and envelope• Comparison with theory of random signal


The field of a SASE FEL (by solving Green’s function) is

[S. Krinsky and Z. Huang, Phys. Rev. ST Accel. Beams 6, 050702 (2003).]

SASE FEL output as a sum of random raidators

.)(exp)(),( 00

eN

ijjttizEztE

Which can be rewritten as

Where, from central limited theorem, R (normal) and (uniform) are independent random variables. Introduce

is the SASE bandwidth

)],(exp[)()( titRtE


SASE FEL output as a sum of random raidators

SASE out put

Where, R has normal and and has uniform random distributions. Introducing,

Under these conditions, it is has been calculated (S. O. Rice, Bell Syst. Tech. J. 24, 46 1945. See Section 3.8.) that at intensity extremes, the distribution function is

>0, maxima; <0, minima.

)],(exp[)()( titRtE

Krinsky, Li, PRE 73, 066501 (2006).


Sample result of statistical calculation

),,,,,( RRR

This corresponds to the probability distribution function

Spike width distribution

.]))/(1()/(23[)(

)(

02/522225

aa

d

a

a

d

dP

Phase =/ distribution at spike maxima (+) and minima (-)

.)]1(3[3

)(2244

d

dp

The constants are a=0.8685, =9.510, =0.7925.

Krinsky, Li, PRE 73, 066501 (2006).


Statistics of FEL dynamics: Statistics of dynamics of thermal light

0 1 2 30.0

0.5

1.0

1.5

2.0

(a)

dp

()/d

=/‹›

exp sim the

0 4 8 12

0.0

0.1

0.2

0.3

0.4

(b)

dp

()/d

= t/‹›

Li et al., PRL 89, 234801 (2002); 91, 243602 (2003).Li et al., APB 80, 31 (2006).

0 1 2 3 4

0.0

0.5

1.0

(a)

dp

+()

/d

='|/

exp sim the

0 2 4 6 80.00

0.05

0.10 (b)

dp

-()/

d

=|'|/

Spike width

’ at local max

Spike Spacing ’ at local min

.)(exp)(),( 00

eN

ijjttizEztE Simulation:


Implications for XFEL: Number of coherent spikes

First time resolved statistics Pulse duration estimate for XFEL

– No methods is envisaged to directly measure the XFEL pulse duraion

– Spectral measurement is straight forward

– With the correlation, one can infer the XFEL pulse duration from the number and width of the spectral spikes

– Idea is being used by DESY

Li et al., APB 80, 31 (2006).










Thomson scattering for ultrashort X-ray pulses

Thomson scattering– Double Doppler frequency shift

Pulse durations, with a ultrafast laser– Head on: bunch length

– Bunch cross section


Small-angle Thomson scatteringX-ray duration determined by laser pulse duration

e-

laser

x-ray

t

Before interaction

During interaction

After interactionShort pulse X-ray generationY. Li, Z. Huang, M. Borland, and S. MiltonPhys Rev. ST-AB 5, 044701 (2002).Khan et al., Proc. PAC 97, 1810 (1997).

30 fs

40 fs

50 fs

25 fs

70 fs

100 fs

50 100 150 200

500

1000

1500

2000

2500

3000

3500

4000

x,

y (m)

25 fs

30 fs

40 fs

50 fs

70 fs

100 fs


Performance: spectra and brightness for 6 Hz APS linac

1.0

1.5

2.0

2.5

3.0

5 10 15 20 25 30 35 400

5

10

15

20

25

Pea

k b

rig

htn

ess

(1020

ph

s-1 m

rad

-2 m

m-2 0

.1%

BW

)

Peak photon energy (keV)

Brightness FW

HM

Du

rati

on

(fs

)

Duration

0 10 20 30 40 50 600.0

0.5

1.0

1.5

2.0

2.5

3.0

Pea

k b

rig

htn

ess

(1020

ph

s-1 m

rad

-2 m

m-2 0

.1%

BW

)

40 keV32 keV

24 keV

16 keV

8 keV

Photon Energy (keV)

Bunch Energy 650 MeVBeta function 1.5 cmEmittance 10 mLaser 20-fs, 2-J @ 800 nm

Sample spectra Brightness and duration


Performance with 6 Hz beam

1E5

3E4

1E4

3E3

50 100 150 200

500

1000

1500

2000

2500

3000

3500

4000

x,

y (m)

1E3

3E3

1E4

3E4

1E5

3E5

1E6

X-ray photon flux (photons s-1 0.1% bandwidth)

1E19 3E181E18

3E171E17

3E19

50 100 150 200

500

1000

1500

2000

2500

3000

3500

4000

x,

y (m)

1E17

3E17

1E18

3E18

1E19

3E19

1E20

Peak spectral brightnessPhotons s-1 mm-2 mrad-2 per 0.1% BW


For APS storage ring? Too high energy but good for G-ray

Table 1 Advanced Photon Source Beam and the laser pulse parameters

Beam Laser

Particles per pulse 1011 (15 nC) 2×1016 (5 mJ)

Electron, photon energy 7 GeV 1.55 eV

Energy spread (rms) 0.1% 0.5%

Pulse duration 45 ps 0.1-1 ps

Repetition rate 6.528 MHz 4 kHz

RMS beam size 92 m×26 m

26 m×26 m

3 4 5 6 70

1

2

3

0 20 40 60 800

10

20

30

(a)

Flu

x (1

03 /s/0

.1%

BW

)

Photon energy (MeV)

(b)

Flu

x (1

09 /s)

Peak photon energy (MeV)

FIG. 1 (a) A -ray spectrum peaked at 5 MeV; (b) the total flux as a function of the peak photon energy. An acceptance angle of 1/is used in the calculation, where is the relativistic factor of the beam. In (b), the peak photon energy is tuned by changing the interaction angle between the laser and the electron beam. Here a laser repetition rate of 4 kHz and an optical cavity with a quality factor of 1000 at 6.52 MHz is considered.

Li et. al., Appl. Phys. Lett. 88, 021113 (2006)


Generating of ultrafast positron beams

Strike a target/sample to generate pairs Detexcting the annihilation gamma to obtain information on defect and

structure change Good for in-situ bulk material structure probe with high temporal

resolutionLi et. al., Appl. Phys. Lett. 88, 021113 (2006), AIP news 789

0 2 40

1

2

3

4

5

Time (ps)

En

erg

y (M

eV)

>106/s










3D laser pulse shaping outline

Beam brightness

– Need for high brightness beams

– Definition brightness and emittance

– Constraints• Cathode emittance: thermal and beam size• Emittance growth

Way to increase brightness

– Using rf photocathode injector• Lower temperature to reduce thermal emittance• Short pulse duration to increase peak brightness• Pulse shaping to compensate for emittance growth

– Other ways • Emittance exchange• Beam cooling• etc


A photoinjector for high brightness beam

D. Dowell et al., “The status of normal conducting RF (NCRF) guns, a summary of the ERL2005 workshop,” NIMA 557, 61 (2005) .

C. Sinclair, ibid, “DC photoemission electron guns as ERL sources ,” p. 69.

D. Janssen et al., ibid, “Technology challenges for SRF guns as ERL sources in view of Rossendorf work ,” p. 80.

Laser

Electrons

Gun

Why high brightness?

– Synchrotron/ERL light sources: more photons and better coherence

– Free-electron lasers: shorter undulators lines and beam energy, 50% reduction in emittance saves 15% of total cost

Solution step one: potocathode rf gun: The electron beam has less

thermal energy High accelerating field at

cathode– DC gun: 5-8 MV/m– RF gun: 40-100 MV/m

The electron beam carries over the laser beam 3-D shape


Brightness, emittance, emittance growth, emittance compensation, and an ellipsoidal beam Brightness

Emittance

Space-charge force and emittance growth

Emittance compensation

With proper arrangement of the solenoid, emittance growth due to linear space-charge force can be fully compensated

An ellipsoidal beam has a linear space-charge field (Reiser’s book)

I

B

2221xppx

mc

2argarg00

1,)(,

1

echspaceotherechspacexx EdtFeEppdtpmc

xx

{


An uniform ellipsoidal beam

Uniform electron density distribution in a ellipsoid Has linear space charge force (M. Reiser, Theory and Design of Charged

Particle Beams, Wiley, New York.)

{


Realization of an Ellipsoid: Luiten Scheme

Pro

– Easy: Need a short pulse (100 fs) with initial parabolic transverse distribution, no longi shaping needed

– Potentially high peak current at the gun exit Con

– Cannot put too many charges: image charge will distort the beam

– Pancake geometry thus larger transverse size: larger cathode emittance to start with

– Short, intense pulse may damage transport optics and cathode

– Fast response precludes many cathode material, stuck with metal How about an ellipsoidal pulse?

J.Luiten, “How to realize uniform 3-dimensional ellipsoidal electron bunches”, Phys.Rev.Letters Aug04


3D laser pulse shaping to generate an ellipsoidal beam

Difficulties– Simultaneous evolving longitudinal and transverse

profiles– Homogeneous in 3-D

Existing methods: pulse stacking, not reallyOur method: real 3-D pulse shaping by

spatiotemporal coupling via dispersion


Ellipsoidal pulse: Gaussian analysis and simulation

11

111)(

)(

1

RRn

f

Y. Li and J. Lewellen, PRL 100, 078401(2008)

-4 0 4 80.0

0.2

0.4

0.6

r (m

m)

(a)

t (ps)

0

0.5

1.0

T

tT

T

tttdttt 1

2/12

00 sin12

)()(

2/12

0 1)(

T

tAtA

10

0

n

ff

2

2/12

0

/1)()(

/1

Tttwt

fzfww R

With ellipsoidal boundaries,

Nees a top-hat transverse profile

t

t

Beam

siz

e

w


Numerical calculation: Fourier optics

Full wave optics (Fresnel diffraction) adapted from Kempe et al. (JOSA B 9, 1158 (1992))

Group velocity dispersion and group velocity delay effect considered up to the second order


The 3D laser pulse at the focal plane of a lens

f=150 mm, a=50 mm, 249 nm, 6 ps FW

-4 0 4 8

0.0

0.5

1.0

0

2

4

6

-0.5

0.0

0.5

-4 0 4 80.0

0.2

0.4

0.6

t (ps)

0

0.5

1.0(d)

t (ps)

(a)

I (ar

b. u

nits)

-0.08 -0.06 -0.04

0.0

0.5

1.0(b)

-4 0 4 80.0

0.2

0.4

0.6

r (m

m)

(c)

t (ps)

0

0.5

1.0

(1

03 rad

)

Li and Lewellen, Phys. Rev Lett, 100, 078401 (2008).


Simulation for the Linear Coherent Light Source (LCLS)

•M. Ferrario et. al., “NEW DESIGN STUDY AND RELATED EXPERIMENTAL PROGRAM FOR THE LCLS RF PHOTOINJECTOR,” Pac 2000, p 1644

Q>=1 nC<=1 mm mrar

(Credit: Dowell, SLAC)


Beam performance: Comparison of space charge field in free space and in the LCLS injector

Free space LCLS

Li and Lewellen, Phys. Rev Lett, in press.


Emittance evolution with booster

0 2 4 6 8 10

0.4

0.8

1.2

Beer can Egg Pancake Shaped

(c)

x (m

m m

rad)

z (m)

Y. Li and J. Lewellen, PRL 100, 078401(2008)


A proof of principle experiment

To show the physics To show technical feasibility Experimental setup

– 800 nm laser, 1 kHz, 10 nJ perpulse, 40 nm bandwidth

– ZnSe lens as the focal lens

– DAZZLER as the phase modulator

– Achromatic lens for transport

C

ALZSL

SF

PP

D

ODL

Figure 1. Schematic of the experiment. Keys: PP: pulse picker; D: AOPDF; SF: achromatic spatial filter; ZSL: ZnSe lens; AL: achromatic image relay lens; ODL: optical delay line; C: camera.


Acousto-optic Programmable Dispersive filter

It launches an acoustic wave along the beam in a birefringent crystal.

The input polarization is diffracted to the other by the sound wave. The frequency that has its polarization rotated depends on the acoustic-wave frequency. Its relative delay at the crystal exit depends on the relative group velocities of the two polarizations. 760 800 840

0.0

0.5

1.0

-3036101316

-1.0 -0.5 0.0 0.5 1.00.0

0.5

1.0

-4-2024

(b)A (ar

b. u

nits)

(nm)

()

(a)

t (ps)


Results with a Gaussian beam with different aperture size

Demonstrated validity of the theory and method Work for the future

– Need large, flat topped beam: more laser energy– Need even more energy for frequency conversion– Adaptive control

-1 0 1 -1 0 1-1 0 1-1 0 1

0.0

0.5

1.0

t (ps)

I (ar

b.u

nits)

P = 12 mm

-30

0

30

r (m

)

P = 2 mm

-30

0

30

P = 3 mm

P = 4 mm

-6 -4 -2 0 2 4 6

-6

-4

-2

0

2

4

6

x (mm)

y (m

m)

Input beam


Publications on laser related work 3D laser pulse shaping and propagation for high brightness beam generation

– Y. Li and J. Lewellen, Phys. Rev. Lett. 100, 078401 (2008).

– Y. Li and S. Chemerisov, Opt. Lett., in press.

– Y. Li and Crowell, Opt. Lett. 32, 93 (2007). Pulse train generation for high power THz radiation

– Y. Li and K. Kim, Appl. Phys. Lett. 92, 014101 (2008);

– Li, Sun and Kim, PRSTAB, in press Laser beam interaction for ultrfast X-ray and Gamma ray generation

– Y. Li, Guo, Liu, and Harkay, Appl. Phys. Lett. 89, 021113 (2006);

– Y. Li, Huang, and Borland, Phys Rev ST AB 5, 044701 (2002). EO application for accelerator

– Y. Li, Appl. Phys. Lett. 88, 251108 (2006). Laser plasma accelerator simulations

– K. Nemeth, et al, Phys. Rev. Lett. 100, 095002 (2008);

– B. Shen, Li, Yu, and J. Cary, Phys. Rev. E 76, 055402 (R) (2007);

– B. Shen, et al., Phys. Plasmas 14, 053115 (2007); FEL diagnostics and Femto statistical optics

– S. Krinsky, Y. Li, PRE 73, 066501 (2006);

– Y. Li et al., Appl.Phys B 80, 31 (2005);

– Y. Li et al, Phys Rev Lett. 91, 243602 (2003);

– Y. Li et al., Phys Rev Lett 89, 234801 (2002); 90, 199903 (2003).


Summary

The marriage of accelerators and lasers is unavoidable and is a rich field of applications, sciences, and challenge, in both enhancing capability of controlling and measuring the beams in a conventional accelerator, and in generating novel light and particle sources.

Documents

Application of ultrafast laser techniques in accelerators Yuelin Li Accelerator Systems Division Argonne National Laboratory [email protected]