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High Energy Electron Acceleration Using Plasmas, 6-10 June , Paris, 2005

Laser Electron AccelerationProject at JAERI

Masaki KandoAdvanced Photon Research Center

Japan Atomic Energy Research Institute (JAERI)

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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, JAERI2) Kyoto University3) High Energy Accelerator Research Organization (KEK)4) The University of Tokyo

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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

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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 L=Ldp (L=n Ldp n:integer is ok?)

1

10

100

1000

1018 1019 1020 1021

RAL (12TW/40fs)

LOA (30TW/33fs)

LBNL (9TW/55fs)

AIST (2TW/50fs)

JAERI/CRIEPI (5.5TW/70fs)

Plasma density (cm-3)

E. Miura et al., J. Plasma Fusion Res. 81 255-260 (2005)

Experiments

S. P. D. Mangles et al., Nature 431, 535 (2004)C. G. R. Geddes et al., Nature 431, 538 (2004)

W. Lu et al., This Workshop

High peak power is required

Not so high peak power is required

A. Yamazaki et al., submitted to PoP

J. Faure et al., Nature 431 (2004)

S. Gordienko & A. Pukhov, Phys. Plasmas 12, 043109 (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

• Peak power > 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 a0=1.7 at 25TW2.0x1019 W/cm2 a0=3.0 at 25TW

• Plasma density 3x1018-1x1020 cm-3

• Target He-gas-jet • length 1.3-10 mm (slit length)

Long-Focus experiment

Goal:Quasi-mono energetic electrons ‘Bubble /Blow-out regime’Test of non-uniform plasma densityBetatron X-ray measurement

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Near-Term Experiment - Diagnosis

• 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 N

aI

magnet size 10cmx10cm

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Experimental setup

We are installing a new big target chamber

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OAP TestWith He-Ne laserAlmost perfect

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2D PIC Simulations

Although 2D simulation underestimates the maximum energy when self-focusing happens, qualitative estimation is valid.

Ne=3x1018 cm-3 Ne=1.7x1019 cm-3

Uniform plasmaa0=1.7

T=23 fs, sx=16µm

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2D PIC Simulations

Ne=1.7x1019 - 8.5x1018cm-3 Ne=1.7x1019 cm-3

Sharp-density transition Parabolic- realistic distribution

a0=1.7T=23 fs, sx=16µm

Narrow

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Schedule

Lasermaintenance

TargetChamber

Experiment

2005 4 5 6 7 8 9 10 11 12

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)

2.1x1019 cm-3

1.1x1019 cm-3

L=2µm

P. Tomassini et al., Phys. Rev. ST 6, 121301 (2003)

No energetic electrons in homogenous plasma

a0=1.3=17fs

ne

Quasi-monoenergetic structure is formed if the length is appropriate.

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Artificial prepulse & High contrast

Demonstration has been done

Next step: controllability & stability

Artificial prepulse

Hydrodynamic codeT. Hosokai et al., PRE 2003

U. Tokyo

Artificial prepulse, ~ns

High Contrast(better than 10-7)•Fast Pockels Cell•Frequency doubling

In the compressor chamber, we will install optics to produce prepulse

Uncompressed Laser

Main pulse~ 40 fs

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Control of gas-jet density

• Compression by shock-wavesControlling a curvature of the wall makes it possible 1

23

2

4.0mm

2

3

4.0mm

1

1.26mm

xy

z

SupersonicgaslayerHigh-densitygasfoilShockwavesfromnozzlewall

-1 1019

0 100

1 1019

2 1019

3 1019

4 1019

5 1019

6 1019

-4 -3 -2 -1 0 1 2 3 4

Z=4.6 mm 305ch

X (mm)

L~100 µm ~ spatial resolution

Better measurement and Wall shape optimization are required

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Preliminary test with density control

Solution1 : Gas-Cell + Supersonic gas-jet

Small aperture

To avoid ‘up-ramp’ density profile

Exit aperture

Lavar typeWall shape

In case of short-focal length, the up-ramp region destroys laser focusing

He Me=5 ρ/ρ0(x10-2)

2.0

1.0

3.0

PlasmaChannelFocusPoint

Shadow

M. UesakaLab.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.