Laser Electron Acceleration
Project at JAERI
Masaki Kando
Advanced Photon Research Center
Japan Atomic Energy Research Institute (JAERI)
1
High Energy Electron Acceleration Using Plasmas, 6-10 June , Paris, 2005
Collaborators
A. Yamazaki1,2), H. Kotaki1), S. Kondo1), T. Homma1), S. Kanazawa1),
K. Nakajima1,3), L.M. Chen1), J. Ma1), H. Kiriyama1), Y. Akahane1),
M. Mori1), Y. Hayashi1), Y. Nakai1), Y. Yamamoto1), K. Tsuji1),
T. Shimomura1) , K. Yamakawa1) , J. Koga1), T. Hosokai4),
A. Zhidkov4), K. Kinoshita4), M. Uesaka4), S. V. Bulanov1),
T. Esirkepov1), M. Yamagiwa1), T. Kimura1), T. Tajima1)
and International Experimental Taskforce (IET) members
1)
APRC, JAERI
2) Kyoto University
3) High Energy Accelerator Research Organization (KEK)
4) The University of Tokyo
2
Table of Contents
1. Introduction
2. Theoretical work on Beam Quality
3. Our Approach to Good quality beams
1. High power laser :Bubble/Blow-out regime
2. Moderate power laser: Gas density control
4. Summary
3
Introduction
JAERI Laser Electron Acceleration Project(2005-2009)
• Demonstration of 1GeV Acceleration
Bubble/blow-out, Fast-Z pinch capillary waveguide,..
• High quality beam production
• Application
- keV X-ray source (compact)
We plan to use wakefield as an undulator
- Pump-probe experiment (Ultrafast science)
4
Route to quasi-monoenergetic electrons
• Bubble regime J. Faure et al., Nature 431 (2004)
Blow-out regime
W. Lu et al., This Workshop
Scaling laws
High peak power is required
• Length matching L=Ldp
(L=n Ldp n:integer is ok?)
S. P. D. Mangles et al., Nature 431, 535 (2004)
C. G. R. Geddes et al., Nature 431, 538 (2004)
Not so high peak power is required
Energy of quasi-monoenergetic peak (MeV)
S. Gordienko & A. Pukhov, Phys. Plasmas 12, 043109 (2005)
1000
Experiments
RAL (12TW/40fs)
LOA (30TW/33fs)
LBNL (9TW/55fs)
AIST (2TW/50fs)
JAERI/CRIEPI (5.5TW/70fs)
100
10
A. Yamazaki et al., submitted to PoP
1
1018
1019
1020
1021
Plasma density (cm-3)
E. Miura et al., J. Plasma Fusion Res. 81 255-260 (2005)
5
Energy spectrum of accelerated electrons
1D Hamiltonian, Motion in 1st wake-period
S.V. Bulanov et al., appeared in Phys.
6
Plasma, soon
Energy spectrum of fast electrons
7
Energy spectrum of fast electrons
8
Transverse emittance
9
Transverse emittance
10
Transverse emittance
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Near-Term Experiment at JAERI
Long-Focus experiment
• Peak power
• Pulse duration
• Focal length
• Spot radius,w0
• Contrast
• Peak intensity
• Plasma density
• Target
• length
> 50 TW
23 fs
775 mm / 450mm
~16µm / ~9 µm
10-6
6.2x1018 W/cm2 a0=1.7 at 25TW
2.0x1019 W/cm2 a0=3.0 at 25TW
3x1018-1x1020 cm-3
He-gas-jet
1.3-10 mm (slit length)
Goal:
Quasi-mono energetic electrons ‘Bubble /Blow-out regime’
Test of non-uniform plasma density
Betatron X-ray measurement
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Near-Term Experiment - Diagnosis
•
Electron
– Charge
– Energy
magnet size 10cmx10cm
Current Transformer
Compact spectrometer
w/Scintillating screen
– High energy detection: Sampling calorimeter
– Pulse duration
• Bolometer (THz detection), Single-shot meas.
by polychromator
•
•
Plasma
– Channeling
Schlieren/shadowgraphy/
Interferometry
X-ray
– Energy
Ross filter and Photon counting on CCD
– Angular distribution Rail system & CCD and/or NaI
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Experimental setup
We are installing a new big target chamber
OAP Test
With He-Ne laser
Almost perfect
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2D PIC Simulations
Although 2D simulation underestimates the maximum energy when self-focusing happens,
qualitative estimation is valid.
Uniform plasma
a0=1.7
T=23 fs, sx=16µm
Ne=3x1018 cm-3
Ne=1.7x1019 cm-3
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2D PIC Simulations
Parabolic- realistic distribution
Sharp-density transition
a0=1.7
T=23 fs,
sx=16µm
Ne=1.7x1019 - 8.5x1018cm-3
Ne=1.7x1019 cm-3
Narrow
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Schedule
2005
Laser
maintenance
4
5
6
7
8
9
10
11
12
Oscillator replacement/ Regen realignment
Power Amp. YAG replacement
Target
Chamber
New big chamber installation
Optics adjustment
Spot, Pulse duration check
Experiment
Shots (Electron/Ion)
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Sharp density transition enhances injection
No energetic electrons in homogenous plasma
L=2µm
2.1x1019 cm-3
ne
a0=1.3
t=17fs
S. V. Bulanov et al., Phys.Rev.E 58, R5257 (1998)
H. Suk et al., Phys. Rev. Lett 8, 1011 (2001)
T. Hosokai et al., Phys. Rev. E 67, 036407 (2003)
P. Tomassini et al., Phys. Rev. ST 6, 121301 (2003)
Quasi-monoenergetic structure is formed if
the length is appropriate.
1.1x1019 cm-3
P. Tomassini et al., Phys. Rev. ST 6, 121301 (2003)
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U. Tokyo
Artificial prepulse & High contrast
Demonstration has been done
Next step: controllability & stability
Artificial prepulse
In the compressor chamber, we will install
optics to produce prepulse
Uncompressed Laser
Main pulse
~ 40 fs
Artificial prepulse, ~ns
Hydrodynamic code
T. Hosokai et al., PRE 2003
High Contrast(better than 10-7)
•Fast Pockels Cell
•Frequency doubling
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Control of gas-jet density
• Compression1 Supersonic
by shock-waves
gas layer
Controlling a curvature of the wall makes it possible
High-density gas foil
2
3 Shockwaves from nozzle wall
6 1019
2
Z=4.6 mm 305ch
5 1019
4 1019
Gas density (cm-3)
z
y
x
4 .0 m m
3 1019
2 1019
1 1019
3
0 100
2
1
-1 1019
-4
-3
-2
-1
0
1
2
3
4
X (mm)
L~100 µm ~ spatial resolution
4 .0 m m
1 .2 6 m m
Better measurement and
Wall shape optimization are required
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Preliminary test with density control
In case of short-focal length, the upramp region destroys laser focusing
To avoid ‘up-ramp’ density profile
Solution1 : Gas-Cell + Supersonic gas-jet
Shadow
FocusPoint Plasma Channel
He
Me=5
Small aperture
Exit aperture
(x10-2)
Lavar type
Wall shape
1.0
2.0
M. Uesaka
Lab.
U. Tokyo
3.0
This configuration will be tested
Solution2 Use longer focal length
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Summary
• Theoretical investigation of energy distribution is performed,
and qualitatively reproduce experimental data.
• Parameter survey will be done around ‘Bubble / Blow-out
regime/’ with JAERI 100 TW, 23 fs laser.
– Laser and target chamber improvement is under way.
• Control of gas-distribution and prepulse are important for
electron acceleration.
– We are developing Gas-jet-nozzle in order to control particle injection
and acceleration for relatively small lasers.
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