laser-ion acceleration with the leaky light sail

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Mitglied der Helmholtz- Gemeinschaft Laser-Ion Acceleration with the Leaky Light Sail in Qiao, Anupam Karmakar, Paul Gibbon , Jülich Supercomputing Centre EMMI Workshop, Speyer, 27 September 2010

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Laser-Ion Acceleration with the Leaky Light Sail. Bin Qiao , Anupam Karmakar , Paul Gibbon , J ü lich Supercomputing Centre. EMMI Workshop, Speyer, 27 September 2010. Forschungszentrum Jülich (FZJ). TEXTOR. JSC. COSY. Plasma Simulation Lab at JSC. Staff Lukas Arnold - PowerPoint PPT Presentation

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Blue Gene Systems at Forschungszentrum Jlich

Laser-Ion Acceleration with the Leaky Light SailBin Qiao, Anupam Karmakar, Paul Gibbon, Jlich Supercomputing Centre

EMMI Workshop, Speyer, 27 September 2010Mitglied der Helmholtz-Gemeinschaft11Forschungszentrum Jlich (FZJ)

JSCTEXTORCOSY27.10.2010 Jlich Supercomputing Centre #2Plasma Simulation Lab at JSCStaffLukas ArnoldAnupam KarmakarBin Qiao (AvH)Paul Gibbon

StudentsBenjamin Berberich (Ph.D., IEF-4)Andreas Galonska (Ph.D.)Helge Hbner (Master)

Robert Speck (Ph.D.)Mathias Winkel (Ph.D.)Andreas Breslau (Dipl., U. Kln)

27.10.2010 Jlich Supercomputing Centre #33Target normal sheath acceleration (TNSA)

Linearly polarized laserElectrons heated to MeV temperature via j x B forceIons accelerated mainly off target rearLow beam density, large divergence, broad energy spread !Variations: microdots; double layers; oblique incidence; BOA;

Wilks et al., PoP (2001) 27.10.2010 Jlich Supercomputing Centre #44Radiation pressure acceleration (RPA)

AB

Circularly polarized or high-intensity LP lasersNo oscillating jxB, so electrons pile up as compressed layerIons are accelerated by the charge-separation, forming bunched layer. Pressure balance Pes = Plaser: ion and electron layers accelerated together as quasi-neutral slab.High beam density & efficiency; monoenergetic spectrum

Macchi et al., PRL (2005,2009) 27.10.2010 Jlich Supercomputing Centre #55RPA scenariosHole-Boring

lLight Sail

Leaky Light Sail

27.10.2010 Jlich Supercomputing Centre #66Hole-boring (HB) regime: semi-infinite foil, d0

neniELx

HB velocityMaximum proton velocity acquired

Robinson et al., PPCF (2009)

depletion regioncompression regionAcceleration via repeated reflectionsfrom HB surface27.10.2010 Jlich Supercomputing Centre #77Light-Sail (LS) RPA for micron-scale foil

Condition: d0 (/)(nc /n0) a0 > c/p

Electrons pile up at the foil rear side in a very thin layer, but are held inside because the laser field vanishes at its rear.Leading edge of Ez bunches ions at the rear (d1 imperfect pressure balance

All foil electrons are accelerated and those near the rear side leak out into vacuum since the laser field does not vanish there.d0 (/)(nc /n0) a0 < c/p

quasi-neutral regionleakageregiondepletion region27.10.2010 Jlich Supercomputing Centre #1313 2D high-resolution PIC simulationswith PIC code ILLUMINATION Nanofoil target: density ne0=nip0=200nc (skin depth ls=11.3nm) thickness l0=8nm net positive charge locally=> Coulomb explosion by trailing edge of Ez. Stable RPA needs accelerated proton layer to be surrounded by an excess of electrons This keeps locally negative charge hence leading edge Ez.local net charge Q27.10.2010 Jlich Supercomputing Centre #1717LLS with multi-species targetA heavy ion with high charge state Z is accompanied with Z times more electrons than a proton for charge balance.

The accelerating proton layer may acquire charge-balancing electrons via the leakage from the heavy ion layer, so that it remains surrounded by an excess number of electrons => avoid Coulomb explosion and preserve stable RPA ?27.10.2010 Jlich Supercomputing Centre #1818 Multi-species nanofoilNanofoil target: electron density ne0=200nc, thickness l0=8nm Coulomb explosion

Proton layer is surrounded by excess electrons=> Stable RPAProton layer poaches electrons from the C6+ layer, maintaining stable RPA

27.10.2010 Jlich Supercomputing Centre #2020Proton energy spectrum and time history typical for RPA

A quasi-monoenergetic proton beam is obtained with density about 0.25nc,peak energy 18MeV, and particle number 108

Typical accelerating curves of RPAThe conversion efficiency is 10%

27.10.2010 Jlich Supercomputing Centre #2121Scaling Density ratio of C6+:H+can be changed from nic0:nip0=8:1 to 1:6 (above which cannot borrow any longer optimum?)

The upper limit of the proton energy :

100MeV proton beam can be obtained by CP laser at intensity 1020W/cm2

B. Qiao et al., Phys. Rev. Lett., in press (October 2010)

Up = 22L2/(2L+imic2)NiL=I0SL laser pulse energy27.10.2010 Jlich Supercomputing Centre #2222