laser plasma accelerators: towards a high quality electron ...laser plasma accelerators: towards a...

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Laser Plasma Accelerators: Towards a high quality electron beam

Victor Malka

Laboratoire d’Optique AppliquéeENSTA-Ecole Polytechnique, CNRS

91761 Palaiseau, FRANCE

Partially supported by CARE-Euroleap-ANR/Accel1 contracts

FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL

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Particle group SPL:J. Faure, Y. Glinec, A. Lifschitz, C. Rechatin

Laboratoire d’Optique Appliquée, ENSTA-Ecole Polytechnique, CNRS,

91761 Palaiseau, FRANCE

Collaborators :

E. Lefebvre, X. Davoine, CEA/DAM Ile-de-France, FranceA. Pukhov, University of Dusseldorf, Germany

Acknowledgement


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SummaryPart 1 : Laser plasma accelerator : motivation

Part 2 : Laser Plasma accelerator as injector : Production of monoenergetic electron beam

Part 3 : New scheme of injection : toward a stable, tunable and quasi monoenergetic electron beam.

Part 4 : Applications

Part 5 :Conclusion and perspectives


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E-field max ≈ few 10 MeV /meter (Breakdown) R>Rmin Synchrotron radiation

Classical accelerator limitations

LEP at CERN

27 km

Circle road

31 km

New medium : the plasma

Energy = Length = $$$

≈ PARIS


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Why is a Plasma useful ?

• Plasma is an Ionized Medium High Electric Fields

epz nE ~~w

• Superconducting RF-Cavities : Ez = 55 MV/m


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How to excite Relativistic Plasma waves?

Broad resonance condition :

τlaser≈ Tp / 2

=>Short laser pulse

The laser wake field

Are Relativistic Plasma waves efficient ?

ez nE ~ Ez = 0.3 GV/m for 1 % Density Perturbation at 1017 cc-1

Ez = 300 GV/m for 100 % Density Perturbation at 1019 cc-1

Tajima and Dawson, PRL (1979)

Phase velocity vfepw=vglaser => close to c Analogy with a boat

laser pulse

Plasma wake

F=- ∇I


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1 meter long RF cavityGain = 50 MeV 100 microns Plasma cavity

Gain = 30 MeV

100 μm

Courtesy of W. Mori & L. da Silva

Compactness of laser plasma accelerators


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Trapping energy : Analogy electron/surfer

Analogy:


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Interaction and dephasing lenghts

Lacc.=πZR

Diffraction limited

ΔWdiff. [MeV] ≈ 580 (λ/λp)/(1+a02/2)1/2 P [TW] ΔWch [MeV] ≈ 60 (λp/w0) P [TW]

Lacc

Guiding : channel or relativistic

electront1 t2 t3

e fγ >> γ >> 1

=> Ldeph. =(λ0 /2)(n c /n e)3/2

L Deph. = λpγf 2


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SummaryPart 1 : Laser plasma accelerator : motivation

Part 2: Laser Plasma accelerator as injector : Production of electron beam

Part 3 : New scheme of injection : toward a stable, tunable and quasi mono-energetic electron beam.




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How to generate an electron beam?Self-modulated Laser Wakefield Scheme

(Andreev, Sprangle, Antonsen 1992)

cτ >> λp

enhances

Wavebreaking occursPL>Pc(GW) = 17 ω02/ωp

2 then

excites

Modena et al., Nature 1995FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL

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Relativistic wave breakingRAL/IC/UCLA/LULI

Multiple satellites : high amplitude plasma wavesbroadening at higher densities

Loss of coherence of the relativistic plasma waves

Forward Raman Spectra

10-1100101102103104105106

-2 -1 0 1 2 3 4 5

Inte

nsity

(U. A

.)spectral shift (ωp)

ne=0.5x1019cm-3

ne=1.5x1019cm-3

Ele

ctro

ns/M

eV 105

106

104

103

101

102

0 20 40 60 80 100 120Energy (MeV)

ne=0.5x1019cm-3

ne=1.5x1019cm-3

Electron spectra

Modena et al., Nature 1995FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL

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Review of some Former Experiments on Electron Beam Generation

Lab Year Process EL Rate Ee

RAL 1995* SMLWF 50 J 20 min 44 MeV

1998 SMLWF 50 J 20 min 100 MeV

NRL 1997 SMLWF 5 J 5 min 30 MeV

MPQ 1999 DLA 0.2 J 10 Hz 10 MeV

LOA 1999 SMLWF 0.6 J 10 Hz 70 MeV

LOA 2001 FLWF 1 J 10 Hz 200 MeVLarge scale, energetic laser, with low repetition rate


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Interaction chamber (inside)

Laser beamelectron beam

50 cm


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Summary of FLWF previous results

V. Malka et al., Science, 298, 1596 (2002)

105

106

107

108

109

1010

0 50 100 150 200Energy (MeV)

Detection Threshold

Num

ber o

f ele

ctro

n (/M

eV/s

r)

Experiments

106

107

108

109

1010

1011

0 50 100 150 200 250Energy (MeV)

Num

ber o

f ele

ctro

n (/M

eV/s

r)

3D PIC simulations


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SMLWF : Multiple e- bunches / FLWF Single e- bunch

V. Malka, Europhysics news, April 2004Ps/fs

Electron bunches

laser

Electric field

Ps

Electron bunch

laserElectron density perturbation

ne/n0-1

Electric field

0

fs


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700

650

Z/λ

20

-20

Y/λ

-20

20

X/λ

Quasi-Mono-energetic Electron BeamsIn homogenous plasma : virtual or real?

0 200 400 E, MeV

t=350

t=450

t=550

t=650t=750

t=850

5 108

1 109Ne / MeV

Time evolution of electron spectrum

monoenergeticelectron beam

VLPL

A.Pukhov & J.Meyer-ter-Vehn, Appl. Phys. B, 74, p.355 (2002)

One stage LPA


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Laser plasma injector

Scheme of principle Experimental set up


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2.0 x 1019cm-3

Divergence = 6 mrad

Spatial quality improvements

6.0 x 1018cm-37.5 x 1018cm-31.0 x 1019cm-3

5.0 x 1019cm-3 3.0 x 1019cm-3


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From SMLFW to Bubble :From Mono to maxwellian spectra

Electron density scan

V. Malka, et al., PoP 2005FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL

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Charge in the peak : 200-300 pC

Energy distribution improvements:The Bubble regime

PIC

Experiment

Divergence = 6 mrad

At LOAJ. Faure et al. Nature (2004)


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S. Mangles et al., C. Geddes et al., J. Faure et al., in Nature 30 septembre 2004


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Quasi-monoenergetic beamsreported in the litterature

Name Article Lab Energy dE/E Charge Ne Intensity tL/Tp Remark[MeV] [%] [pC]

Mangles Nature (2004) RAL 73 6 22 20 2,5 1,6Geddes Nature (2004) L'OASIS 86 2 320 19 11 2,2 ChannelFaure Nature (2004) LOA 170 25 500 6 3 0,7Hidding PRL (2006) JETI 47 9 0,32 40 50 4,6Hsieh PRL (2006) IAMS 55 336 40 2,6Hosokai PRE (2006) U. Tokyo 11,5 10 10 80 22 3,0 PreplasmaMiura APL (2005) AIST 7 20 432E-6 130 5 5,1Hafz PRE (2006) KERI 4,3 93 200 28 1 33,4Mori ArXiv (2006) JAERI 20 24 0,8 50 0,9 4,5Mangles PRL (2006) Lund LC 150 20 20 5 1,4

[x1018/cm3] [x1018 W/cm2]

Several groups have obtained quasi monoenergetic e beam but at higher density (τL>τp)


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Summary

Part 1 : Laser plasma accelerator : motivation

Part 2: Laser Plasma accelerator as injector : Production of mono-energetic electron beam

Part 3 : New scheme of injection : toward a stable, tunable and quasi mono-energetic electron beam.




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Controlling the injection

E. Esarey et al, PRL 79, 2682 (1997), G. Fubiani et al. (PRE 2004)

Ponderomotive force of beatwave: Fp ~ 2a0a1/λ0 (a0 et a1 can be “weak”)Boost electrons locally and injects themINJECTION IS LOCAL and IN FIRST BUCKET

A second laser beam is used to heat electrons

Onde Plasma

Pump beam Injection beam

Beatwave

Injection phase

Trapped electrons

Acceleration phase


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Experimental set up

Lanex

Injection beam130 mJ, 30 fs φfwhm=28× 23 µmI ~ 4×1017 W/cm2

Pump beam670 mJ, 30 fs, φfwhm=21×18 µmI ~ 4×1018 W/cm2


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Very stable quasi-mono energetic electron beam


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Controlling the bunch energy by controlling the acceleration length

By changing delay between pulses: • Change collision point• Change effective acceleration length• Tune bunch energy

Pump beam Injection beam

Gas jet

2 mm


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Tunable monoenergetic beampump injection

pump injection

late injection

early injection

pump injection

middle injection

Zinj=225 μm

Zinj=125 μm

Zinj=25 μm

Zinj=-75 μm

Zinj=-175 μm

Zinj=-275 μm

Zinj=-375 μm

J. Faure et al., Nature 2006FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL

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Tunable mono-energetic electrons beam

190 MeV gain in 700 µm: E=270 GV/mCompare with Emax=mcwp/e=250 GV/m at ne=7.5×1018 cm-3

0

50

100

150

200

250

300

0

5

10

15

20

25

30

35

-200 -100 0 100 200 300 400 500

Pea

k E

nerg

y (M

eV)

δE/E (%

)

-zinj

(µm)

spectrometer resolution δE/E ~ 5 %

δE/EE

peak


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• Charge can be tuned byControlling Heating electrons processes

Changing intensity of injection beam: smaller a1 means less heating and less trapping

• Energy spread can be tuned byDecreasing the phase space volume Vtrap of trapped electrons by changing a1.Changing the ratio cτ/λp by changing ne ( by changing λp)

In practice, energy spread and charge are correlated:Decreasing a1 decreases the charge but also Vtrap, and in consequence the energy spread

Tuning the charge & the energy spread

Evolution of injection volume with a1 for a0 = 2, ne = 7.1018cm-3. Fields are computed for the 1D case and the beatwaveseparatrix corresponds to the circular polarization case.

a1=0.4 a1=0.1


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Charge from 60 pC to 5 pC

ΔE from 20 to 5 MeV

Tuning the charge and the energy spread with injection beam intensity a1

a1=0.4

a1=0.1


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Collaboration with LLR* for resolving small energy spread beams

In collaboration with A. Specka, H. VideauLLR, CNRS, Ecole Polytechnique

LANEX screensPermanent dipolequadripolesGas jet

transport / focusing

dispersion / imagingResolution < 1 % expected


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1% energy spread beams

C. Rechatin et al., submitted to Nature PhysicsFRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL

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Part 1 : Laser plasma accelerator : motivation

Part 2 : Laser Plasma accelerator as injector : Production of mono-energetic electron beam

Part 3 : New scheme of injection : towards a stable, tunableand quasi mono-energetic electron beam.



Summary


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In collaboration with CEA/DAM

Material science: γ-ray radiography

High resolution radiography of dense object with a low divergence, point-like electron source

Glinec et al., PRL 94 025003 (2005)FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL

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γ-radiography results20mm

Cut of the object in 3D

•Spherical hollow object in

tungsten with sinusoidal

structures etched on the inner

part.

Measured Calculated

Source size estimation : 450 umGlinec et al., PRL 94 025003 (2005)


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Medical application : Radiotherapy

VHE ELECTRONS


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VHE Radiation Therapy

Depth in tissue

VHE dose

Reduced dose in save cells

Deep treatment

Good lateral contrast

tumor

tumor

VHE

Dos

e


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A comparison of dose deposition with 6 MeV X ray an improvement of the quality of a clinically approved prostate treatment plan. While the target coverage is the same or even slightly better for 250 MeV electrons compared to photons the dose sparing of sensitive structures is improved (up to 19%).

A typical transversal dose distribution with 7 beams.

Electrons Photons Difference

Improved treatment with electrons

T. Fuchs, DKFZ in preparationFRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL

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Fundamental aspect : fs radiolysisH2O (e-

s, OH., H2O2, H3O+, H2, H.) e-

Very important for:• Biology• Ionizing radiations effects

B. Brozek-Pluska et al., Radiation and Chemistry, 72, 149-159 (2005)**Ar.


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Compact XFEL: towards a bright X ray source

Applications: study of complex structures (X-ray diffraction, EXAFS) But fs time scale

θ ~ mrad

10cm

Reduction of acceleratorReduction of the undulator


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Conclusions / perspectivesSUMMARY• Optical injection by colliding pulse: it works !• Monoenergetic beams trapped in first bucket • Enhances dramatically stability• Energy is tunable: 15-300 MeV• Charge up to 80 pC in monoenergetic bunch• dE/E down to 5 % (spectrometer resolution), dE ~ 10-20 MeV• Duration shorter than 10 fs.

PERSPECTIVES• Combine with waveguide: tunable up to few GeV’s with dE/E ~ 1 %• Design future accelerators• Model the problem for further optimization: higher charge• Stable source:

extremely important • accelerator development (laser based accelerator design)• light source development for XFEL• applications (chemistry, radiotherapy, material science)


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Laser plasma accelerator : Wonderful tool for Science and for Academic activities

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laser plasma accelerators: towards a high quality electron ...laser plasma accelerators: towards a...

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