Transcript Laser plasma accelerator Experiment -Report-

The 12th Advanced Accelerator Workshop
July 10-15, 2006, Lake Geneva
2006.7.11
Characteristics of quasi-monoenergetic
electron beam produced by
3 TW, 70 fs laser
Masaki Kando
Advanced Photon Research Center (APR)
Quantum Beam Science Directorate (QuBS)
Japan Atomic Energy Agency (JAEA)
Collaborators
JAEA
M. Mori, I. Daito, Y. Hayashi, L. M. Chen, K. Ogura, H. Kotaki,
A. Pirozhkov, J. Ma, Y. Fukuda, A. Sagisaka,
T. Zh. Esirkepov, A. Yamazaki, S. Kondo, T. Homma,
K. Nakajima, H. Daido, S. V. Bulanov, T. Kimura
Univ. of Tokyo
T. Hosokai, K. Kinoshita, A. Zhidkov, M. Uesaka
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Table of Contents
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Introduction
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Recent Experimental Results
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Laser Wakefield Acceleration(skip)
Previous results(skip)
Laser system at JAEA
Quasi-monoenergetic electron generation
Repeatability
Comparison with simulations
Ongoing Experiments
Summary
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JLITE-X laser system
JLITE-X (abbreviation)
= JAEA Laser system
for Laser-matter InteracTion Experiment
Output Energy: >200 mJ (on target)
Pulse Width: <70 fs (FWHM)
Peak Power: >3 TW
Repetition Rate: 10Hz
• Optimized to reduce ASE (10-5)
• Pointing stabilizer < ± 10
µrad
• Single-shot operation
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Experimental setup
f/13
f=650mm
Laser parameter:
OAP
Pulse duration: 70 fs
Probe beam
3TW laser beam
Colliamator slit
Laser energy: 210 mJ
Spot diameter: 25µm(1/e2)
(Concentration: 55% )
Laser intensity in vacuum:
E-beam
4x1017 (Averaged )
8x1017 W/cm2(Peak)
Electromagnet
Rayleigh length: 400 um
Target:
Measurement:
He gasjet (super sonic gasjet): 1.2mm
x 10 mm nozzle
Electron spectrum
Scale length of the gasjet: 600 um
Laser propagation with probe beam
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Typical image of the Quasi-monoenergetic
electron beam
Electron density: 4.7x1019 cm-3
Collimator acceptance 1.5 msr
1.2 105
electrons/0.10dMeV
deconvolution
electrons number/0.10MeV
1.0 105
8.0 104
6.0 104
4.0 104
2.0 104
Typical energy resolved e-beam image
(Image was taken by using IP)
Energy:
Energy Spread:
Electron Yield:
Divergence :
0.0
5
10
15
20
25
30
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E[MeV]
Energy distribution of the electron beam
～20(19.6)MeV
4.0 MeV
0.8 pC (Max. ~ 8 pC)
4.6 mrad
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Emittance estimation
Normalized emittance
eN= 0.7 p mm mrad
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Electron Beam emittance ε
e=s1 (s22-s12) /L ～ s1 s2 / L
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Normalized Emittance εN
eN=egb
s1 : beam size (rms) at generation point (= 12.5 um /2 supposed as a laser spot diameter)
s2: beam size (rms) at any observation point
(= 4.5 mm /2 )
L:
(= 757.5 mm)
Distance between generation point
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Energy distribution changes as
a function of the plasma density
Strongly Modulated
Broaden
(peak energy is held)
peak energy is increased
(peak energy is 20 MeV)
Quasi-Mono
(peak energy is 8.5 MeV)
Fine tuning of the plasma density can control the peak energy of electron beams.
Now, we are measuring this feature on detail.
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Single-shot measurement with
Phosphor screen and ICCD Camera
Spatial profile measurement of electron beams
Due to peak intensity was saturated
8.4 mrad (horizontal)
<6.4 mrad
x 6.4 mrad (vertical)
10 mrad
<8.4 mrad
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Reproducibility of QME
Results of a sequence of 66 shots
Divergence
Note that we DO NOT choose suitable shots!
Ne=4.7x1019cm-3
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Energy
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Reproducibility of QME (cont’d)
Example
In a sequence of 66shots
Type of Energy Distribution
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No.of shots
Quasi-Mono (peak)
25 (38%)
Quasi-Mono (Not clear peak)
12 (18%)
Maxwellian
27 (41%)
Undetectable
2 (3%)
Peak energy 6-20.8 MeV (avg. 11 MeV), 20-48%
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2D-PIC simulation of SMWFA Regime
Position of the
Laser Pulse Front
Ez
“snake” in the ion density
Ni
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Energy vs. Plasma density
a)
b)
experiment
simulations
Electron energy spectrum versus plasma density
a) Experimental data and b) Simulation results
1. ne = 4.1 × 1019cm−3;
2. ne = 4.7 × 1019cm−3;
3. ne = 5× 1019cm−3;
4. ne = 6.6× 1019cm−3.
The 2D-PIC simulation reproduces experimentally obtained data.
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Present Experimental Setup
Plasma diagnosis
(shadowgraph,interferometry)
Probe pulse
(100fs, 820nm)
Transmitted Source Monitor
Driver Laser
(200mJ, 70fs, 820nm)
(spectrum, spot)
UV-VIS
Spectrometer
Electron
Spectrometer
X-ray Pinhole
Camera
Source Pulse
Grazing Incidence
Spectrometer
(X-ray CCD)
(4-10mJ, 100fs, 820nm)
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Ongoing Experiments
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Proof-of-principle of Flying Mirror Concepts
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Optical Injection using Colliding scheme
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E. Esarey et al., Phy. Rev. Lett. 79, 2682 (1997)
H. Kotaki et al., Phys. Plasmas 11, 3296 (2004)
Thomson scattering X-ray generation
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S. V. Bulanov et al., Phys. Rev. Lett. 91, 085001 (2003)
H. Schwoerer et al., Phys. Rev. Lett. 96, 014802 (2006)
In particular, measure evolution of electron energy
THz radiation from Solitons
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T. Zh. Esirkepov et al., JETP Lett. 68, 36 (1998); PRL 92, 255001
(2004)
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Summary
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Collimated, 20MeV quasi-monoenergetic
electron beam have been produced with a
relatively small laser and a low vacuum
intensity.
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2D-PIC results explain well the experimental
results.
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Next step: Improve stability
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Single-shot, Online ESM
Example of QME data
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Repeatable production of QME!
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