Laser Electron Acceleration Project at JAERI Masaki Kando Advanced Photon Research Center Japan Atomic Energy Research Institute (JAERI)

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Laser Electron AccelerationProject at
JAERIMasaki KandoAdvanced Photon Research
CenterJapan Atomic Energy Research Institute
(JAERI)
High Energy Electron Acceleration Using Plasmas,
6-10 June , Paris, 2005
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Collaborators

• 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),
• 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

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Table of Contents

• Introduction
• Theoretical work on Beam Quality
• Our Approach to Good quality beams
• High power laser Bubble/Blow-out regime
• Moderate power laser Gas density control
• Summary

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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)
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Route to quasi-monoenergetic electrons

• Bubble regime
• Blow-out regime
• Scaling laws
• Length matching LLdp (Ln Ldp ninteger is ok?)

J. Faure et al., Nature 431 (2004) S. Gordienko
A. Pukhov, Phys. Plasmas 12, 043109 (2005)
Experiments
W. Lu et al., This Workshop
High peak power is required
S. P. D. Mangles et al., Nature 431, 535
(2004) C. G. R. Geddes et al., Nature 431, 538
(2004)
A. Yamazaki et al., submitted to PoP
Not so high peak power is required
E. Miura et al., J. Plasma Fusion Res. 81 255-260
(2005)
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Energy spectrum of accelerated electrons 1D
Hamiltonian, Motion in 1st wake-period
S.V. Bulanov et al., appeared in Phys. Plasma,
soon
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Energy spectrum of fast electrons
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Energy spectrum of fast electrons
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Transverse emittance
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Transverse emittance
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Transverse emittance
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Near-Term Experiment at JAERI
Long-Focus experiment
Peak power gt 50 TW Pulse duration 23 fs
Focal length 775 mm / 450mm Spot
radius,w0 16µm / 9 µm Contrast 10-6 Peak
intensity 6.2x1018 W/cm2 a01.7 at
25TW 2.0x1019 W/cm2 a03.0 at 25TW Plasma
density 3x1018-1x1020 cm-3 Target He-gas-jet
length 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
magnet size 10cmx10cm

• Electron
• Charge Current Transformer
• Energy 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 a01.7 T23 fs, sx16µm
Ne3x1018 cm-3
Ne1.7x1019 cm-3
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2D PIC Simulations
Parabolic- realistic distribution
Sharp-density transition
a01.7 T23 fs, sx16µm
Ne1.7x1019 cm-3
Ne1.7x1019 - 8.5x1018cm-3
Narrow
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Schedule
2005 4 5 6 7 8 9 10 11
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Laser maintenance Target Chamber Experimen
t
Oscillator replacement/ Regen realignment
Power Amp. YAG replacement
New big chamber installation
Optics adjustment
Spot, Pulse duration check
Shots (Electron/Ion)
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Sharp density transition enhances injection
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)
No energetic electrons in homogenous plasma
Quasi-monoenergetic structure is formed if the
length is appropriate.
a01.3 t17fs
L2µm
2.1x1019 cm-3
1.1x1019 cm-3
ne
P. Tomassini et al., Phys. Rev. ST 6, 121301
(2003)
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Artificial prepulse High contrast
U. Tokyo

• 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
High Contrast(better than 10-7) Fast Pockels
Cell Frequency doubling
Hydrodynamic code T. Hosokai et al., PRE 2003
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Control of gas-jet density

• Compression by shock-waves

Controlling a curvature of the wall makes it
possible
L100 µm spatial resolution Better measurement
and Wall shape optimization are required
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Preliminary test with density control
In case of short-focal length, the up-ramp region
destroys laser focusing
To avoid up-ramp density profile
Solution1 Gas-Cell Supersonic gas-jet
Exit aperture
Small aperture
Lavar type Wall shape
M. Uesaka Lab. U. Tokyo
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.