| 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 | Bremsstrahlung emission from high power laser interactions with constrained targets for industrial radiography显示文摘Laser-solid interactions are highly suited as a potential source of high energy X-rays for nondestructive imaging.A bright,energetic X-ray pulse can be driven from a small source,making it ideal for high resolution X-ray radiography.By limiting the lateral dimensions of the target we are able to confine the region over which X-rays are produced,enabling imaging with enhanced resolution and contrast.Using constrained targets we demonstrate experimentally a(20±3)μm X-ray source,improving the image quality compared to unconstrained foil targets.Modelling demonstrates that a larger sheath field envelope around the perimeter of the constrained targets increases the proportion of electron current that recirculates through the target,driving a brighter source of X-rays. | C.D.Armstrong C.M.Brenner C.Jones D.R.Rusby Z.E.Davidson Y.Zhang J.Wragg S.Richards C.Spindloe P.Oliveira M.Notley R.Clarke S.R.Mirfayzi S.Kar Y.Li T.Scott P.McKenna D.Neely | 2019 | High Power Laser Science and Engineering2019，7，2： | 0 |
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