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| 1 | Observation and modelling of stimulated Raman scattering driven by an optically smoothed laser beam in experimental conditions relevant for shock ignition显示文摘We report results and modelling of an experiment performed at the Target Area West Vulcan laser facility,aimed at investigating laser±plasma interaction in conditions that are of interest for the shock ignition scheme in inertial confinement fusion(ICF),that is,laser intensity higher than 10^(16) W/cm^(2) impinging on a hot(T>1 keV),inhomogeneous and long scalelength pre-formed plasma.Measurements show a significant stimulated Raman scattering(SRS)backscattering(;%-20%of laser energy)driven at low plasma densities and no signatures of two-plasmon decay(TPD)/SRS driven at the quarter critical density region.Results are satisfactorily reproduced by an analytical model accounting for the convective SRS growth in independent laser speckles,in conditions where the reflectivity is dominated by the contribution from the most intense speckles,where SRS becomes saturated.Analytical and kinetic simulations well reproduce the onset of SRS at low plasma densities in a regime strongly affected by non-linear Landau damping and by filamentation of the most intense laser speckles.The absence of TPD/SRS at higher densities is explained by pump depletion and plasma smoothing driven by filamentation.The prevalence of laser coupling in the low-density profile justifies the low temperature measured for hot electrons(7-12 keV),which is well reproduced by numerical simulations. | G.Cristoforetti S.Hüller P.Koester L.Antonelli S.Atzeni F.Baffigi D.Batani C.Baird N.Booth M.Galimberti K.Glize A.Héron M.Khan P.Loiseau D.Mancelli M.Notley P.Oliveira O.Renner M.Smid A.Schiavi G.Tran N.C.Woolsey L.A.Gizzi | 2021 | High Power Laser Science and Engineering2021，9，4： | 1 |
| 2 | Time evolution of stimulated Raman scattering and two-plasmon decay at laser intensities relevant for shock ignition in a hot plasma显示文摘Laser–plasma interaction(LPI)at intensities 1015–1016 W·cm^-2 is dominated by parametric instabilities which can be responsible for a significant amount of non-collisional absorption and generate large fluxes of high-energy nonthermal electrons.Such a regime is of paramount importance for inertial confinement fusion(ICF)and in particular for the shock ignition scheme.In this paper we report on an experiment carried out at the Prague Asterix Laser System(PALS)facility to investigate the extent and time history of stimulated Raman scattering(SRS)and two-plasmon decay(TPD)instabilities,driven by the interaction of an infrared laser pulse at an intensity^1.2×1016 W·cm^-2 with a^100μm scalelength plasma produced from irradiation of a flat plastic target.The laser pulse duration(300 ps)and the high value of plasma temperature(~4 ke V)expected from hydrodynamic simulations make these results interesting for a deeper understanding of LPI in shock ignition conditions.Experimental results show that absolute TPD/SRS,driven at a quarter of the critical density,and convective SRS,driven at lower plasma densities,are well separated in time,with absolute instabilities driven at early times of interaction and convective backward SRS emerging at the laser peak and persisting all over the tail of the pulse.Side-scattering SRS,driven at low plasma densities,is also clearly observed.Experimental results are compared to fully kinetic large-scale,two-dimensional simulations.Particle-in-cell results,beyond reproducing the framework delineated by the experimental measurements,reveal the importance of filamentation instability in ruling the onset of SRS and stimulated Brillouin scattering instabilities and confirm the crucial role of collisionless absorption in the LPI energy balance. | G.Cristoforetti L.Antonelli D.Mancelli S.Atzeni F.Baffigi F.Barbato D.Batani G.Boutoux F.D'Amato J.Dostal R.Dudzak E.Filippov Y.J.Gu L.Juha O.Klimo M.Krus S.Malko A.S.Martynenko Ph.Nicolai V.Ospina S.Pikuz O.Renner J.Santos V.T.Tikhonchuk J.Trela S.Viciani L.Volpe S.Weber L.A.Gizzi | 2019 | High Power Laser Science and Engineering2019，7，3： | 0 |
| 3 | Bright betatron radiation from direct-laseraccelerated electrons at moderate relativistic laser intensity显示文摘Direct laser acceleration(DLA)of electrons in a plasma of near-critical electron density(NCD)and the associated synchrotron-like radiation are discussed for moderate relativistic laser intensity(normalized laser amplitude a0≤4.3)and ps length pulse.This regime is typical of kJ PW-class laser facilities designed for high-energy-density(HED)research.In experiments at the PHELIX facility,it has been demonstrated that interaction of a 1019 W/cm2 sub-ps laser pulse with a sub-mm length NCD plasma results in the generation of high-current well-directed superponderomotive electrons with an effective temperature ten times higher than the ponderomotive potential[Rosmej et al.,Plasma Phys.Controlled Fusion 62,115024(2020)].Three-dimensional particle-in-cell simulations provide good agreement with the measured electron energy distribution and are used in the current work to study synchrotron radiation from the DLA-accelerated electrons.The resulting x-ray spectrum with a critical energy of 5 keV reveals an ultrahigh photon number of 731011 in the 1–30 keV photon energy range at the focused laser energy of 20 J.Numerical simulations of betatron x-ray phase contrast imaging based on the DLA process for the parameters of a PHELIX laser are presented.The results are of interest for applications in HED experiments,which require a ps x-ray pulse and a high photon flux. | O.N.Rosmej X.F.Shen A.Pukhov L.Antonelli F.Barbato M.Gyrdymov M.M.Gunther S.Zahter V.S.Popov N.G.Borisenko N.E.Andreev | 2021 | Matter and Radiation at Extremes2021，6，4： | 0 |
| 4 | Proton deflectometry of a capacitor coil target along two axes显示文摘A developing application of laser-driven currents is the generation of magnetic fields of picosecond-nanosecond duration with magnitudes exceeding B=10 T.Single-loop and helical coil targets can direct laser-driven discharge currents along wires to generate spatially uniform,quasi-static magnetic fields on the millimetre scale.Here,we present proton deflectometry across two axes of a single-loop coil ranging from 1 to 2 mm in diameter.Comparison with proton tracking simulations shows that measured magnetic fields are the result of kiloampere currents in the coil and electric charges distributed around the coil target.Using this dual-axis platform for proton deflectometry,robust measurements can be made of the evolution of magnetic fields in a capacitor coil target. | P.Bradford M.P.Read M.Ehret L.Antonelli M.Khan N.Booth K.Glize D.Carroll R.J.Clarke R.Heathcote S.Ryazantsev S.Pikuz C.Spindloe J.D.Moody B.B.Pollock V.T.Tikhonchuk C.P.Ridgers J.J.Santos N.C.Woolsey | 2020 | High Power Laser Science and Engineering2020，8，2： | 0 |
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