Laser Electron AccelerationProject at JAERI

Masaki KandoAdvanced Photon Research CenterJapan Atomic Energy Research Institute (JAERI)

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

CollaboratorsYamazaki1,2), 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, JAERI2) Kyoto University3) High Energy Accelerator Research Organization (KEK)4) The University of Tokyo

Table of ContentsIntroductionTheoretical work on Beam QualityOur Approach to Good quality beamsHigh power laser :Bubble/Blow-out regime Moderate power laser: Gas density controlSummary

IntroductionJAERI Laser Electron Acceleration Project(2005-2009) Demonstration of 1GeV AccelerationBubble/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)

Route to quasi-monoenergetic electrons Bubble regime Blow-out regime

Scaling laws

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

E. Miura et al., J. Plasma Fusion Res. 81 255-260 (2005)ExperimentsS. P. D. Mangles et al., Nature 431, 535 (2004)C. G. R. Geddes et al., Nature 431, 538 (2004)W. Lu et al., This WorkshopHigh peak power is requiredNot so high peak power is requiredA. Yamazaki et al., submitted to PoPJ. Faure et al., Nature 431 (2004)S. Gordienko & A. Pukhov, Phys. Plasmas 12, 043109 (2005)

Energy spectrum of accelerated electrons 1D Hamiltonian, Motion in 1st wake-periodS.V. Bulanov et al., appeared in Phys. Plasma, soon

Energy spectrum of fast electrons

Energy spectrum of fast electrons

Transverse emittance

Transverse emittance

Transverse emittance

Near-Term Experiment at JAERI Peak power > 50 TW Pulse duration 23 fs Focal length775 mm / 450mm Spot radius,w0~16m / ~9 m Contrast10-6 Peak intensity6.2x1018 W/cm2 a0=1.7 at 25TW2.0x1019 W/cm2 a0=3.0 at 25TW Plasma density3x1018-1x1020 cm-3 TargetHe-gas-jet length1.3-10 mm (slit length)Long-Focus experimentGoal:Quasi-mono energetic electrons Bubble /Blow-out regimeTest of non-uniform plasma densityBetatron X-ray measurement

Near-Term Experiment - DiagnosisElectron ChargeCurrent TransformerEnergy Compact spectrometer w/Scintillating screenHigh energy detection: Sampling calorimeterPulse duration Bolometer (THz detection), Single-shot meas. by polychromator

PlasmaChanneling Schlieren/shadowgraphy/ Interferometry

X-rayEnergyRoss filter and Photon counting on CCDAngular distributionRail system & CCD and/or NaI

magnet size 10cmx10cm

Experimental setupWe are installing a new big target chamberOAP TestWith He-Ne laserAlmost perfect

2D PIC Simulations Although 2D simulation underestimates the maximum energy when self-focusing happens, qualitative estimation is valid.Ne=3x1018 cm-3Ne=1.7x1019 cm-3Uniform plasmaa0=1.7T=23 fs, sx=16m

2D PIC Simulations Ne=1.7x1019 - 8.5x1018cm-3Ne=1.7x1019 cm-3Sharp-density transitionParabolic- realistic distributiona0=1.7T=23 fs, sx=16mNarrow

ScheduleLasermaintenance

TargetChamber

Experiment

2005 4 5 6 7 8 9 10 11 12Oscillator replacement/ Regen realignmentPower Amp. YAG replacementNew big chamber installationOptics adjustmentSpot, Pulse duration checkShots (Electron/Ion)

Sharp density transition enhances injectionS. 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-31.1x1019 cm-3L=2mP. Tomassini et al., Phys. Rev. ST 6, 121301 (2003)No energetic electrons in homogenous plasmaa0=1.3t=17fsneQuasi-monoenergetic structure is formed if the length is appropriate.

Artificial prepulse & High contrastDemonstration has been doneNext step: controllability & stability Artificial prepulse

Hydrodynamic codeT. Hosokai et al., PRE 2003U. TokyoArtificial prepulse, ~nsHigh Contrast(better than 10-7)Fast Pockels CellFrequency doublingIn the compressor chamber, we will install optics to produce prepulseUncompressed LaserMain pulse~ 40 fs

Control of gas-jet densityCompression by shock-wavesControlling a curvature of the wall makes it possible L~100 m ~ spatial resolution

Better measurement and Wall shape optimization are required

Preliminary test with density controlSolution1 : Gas-Cell + Supersonic gas-jetSmall apertureTo avoid up-ramp density profileExit apertureLavar typeWall shapeIn case of short-focal length, the up-ramp region destroys laser focusing M. UesakaLab.U. TokyoThis configuration will be testedSolution2 Use longer focal length

SummaryTheoretical 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.