L O A Laser Plasma Accelerators: Towards a high quality electron beam Victor Malka Laboratoire d’Optique Appliquée ENSTA-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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Laser Plasma Accelerators: Towards a high quality electron ...Laser Plasma Accelerators: Towards a high quality electron beam Victor Malka Laboratoire d’Optique Appliquée ENSTA-Ecole
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L O A
Laser Plasma Accelerators: Towards a high quality electron beam
L O A FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
L O ALOA
Very stable quasi-mono energetic electron beam
FRISNO 10, February 9-13 (2009) Ein Geidi, ISRAEL
L O A
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
L O ALOA
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