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L O A
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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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Trapping energy : Analogy electron/surfer
Analogy:
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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.
Part 4 : Applications
Part 5 :Conclusion and perspectives
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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Interaction chamber (inside)
Laser beamelectron beam
50 cm
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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Laser plasma injector
Scheme of principle Experimental set up
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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)
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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S. Mangles et al., C. Geddes et al., J. Faure et al., in Nature 30 septembre 2004
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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)
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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.
Part 4 : Applications
Part 5 :Conclusion and perspectives
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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Very stable quasi-mono energetic electron beam
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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.
Part 4 : Applications
Part 5 :Conclusion and perspectives
Summary
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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)
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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Medical application : Radiotherapy
VHE ELECTRONS
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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.
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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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)
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
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Laser plasma accelerator : Wonderful tool for Science and for Academic activities
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FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL