Matter and Radiation at Extremes, Volume. 8, Issue 2, 025901(2023)

Accounting for speckle-scale beam bending in classical ray tracing schemes for propagating realistic pulses in indirect drive ignition conditions

C. Ruyer1...2,a), P. Loiseau1,2, G. Riazuelo1,2, R. Riquier1, A. Debayle1,2, P. E. Masson-Laborde1,2 and O. Morice1 |Show fewer author(s)
Author Affiliations
  • 1CEA, DAM, DIF, F-91297 Arpajon, France
  • 2CEA, LMCE, Université Paris-Saclay, 91680 Bruyères-le-Châtel, France
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    Figures & Tables(9)
    (a) Deflection rate dθ/dx as a function of time as predicted by Eqs. (16) and (17) for a C6+ plasma for various Mach numbers in the fluid [Eq. (7)] and kinetic formalism [Eq. (5)]. (b) Gaussian deflection rate averaged over τSSD = 7 ps, ⟨dθ/dx⟩τSSD, as predicted by Eqs. (19) and (23) (using S = 1 and β = 1) for He2+ (blue lines), C6+ (red lines), and Au50+ (black lines) plasmas as a function of Mach number. Three-dimensional predictions obtained with Hera are superimposed as red circles (see Appendix A for details). The laser has an averaged intensity of I0 = 1 × 1015 W/cm2, and λ0 = 0.35 µm, f♯ = 8, Te = 2.5 keV, Ti = 1 keV, and ne = 0.1nc.
    Temporal evolution of the beam centroid defined though Eq. (2) in the 3D Parax simulations with ωm = 2π × 14.25 GHz and for Δ = 5.1 for TSSD ⊥vd (blue line), LSSD (green line), TSSD ‖vd (red line), and TSSD ⊥vd + PS (magenta line).
    Centroid displacement after 2 mm of propagation as predicted by the theory (lines) and by simulations (symbols). The plasma is composed of He2+ with Te = 2 keV, ZiTe/Ti = 8, M0 = 0.9, and I0 = 2 × 1014 W/cm2. In (a), the 2D centroid displacement Δy is plotted as a function of f♯ with a fixed TSSD = 3.7 ps (or a modulation depth of Δ = 9), while in (b), f♯ = 8.88 is fixed and TSSD varies. In (a), the predictions from the ray tracing scheme and from Eq. (19) with S = 1.7 and β = 2 are shown by the triangles and the black solid line, respectively. A curve of y ∝ 1/f♯ is superimposed as the black dashed line, while the results of the 3D paraxial Parax simulation for the case TSSD ⊥vd are shown by the black circles. In (b), the predictions of Eq. (45) of Ref. 65 are shown by the red dashed line. The cases TSSD ‖vd, TSSD ⊥vd, and LSSD correspond to (S, β) = (1.7, 1), (1.7, 2), and (S, β) = (6, 0.8), respectively. The case with PS corresponds to (S, β) = (0.8, 3).
    Hydrodynamic simulation performed with the Troll code38 for the Hybrid B NIF Shot N181209,55–57 illustrated in the frame of the inner cone (y = 0 is the main inner cone axis), at 6 ns. (a) Total power of main laser drive. (b) Averaged local ionization number ⟨Zi⟩ (the color map is saturated to 10). (c) Electron temperature Te (keV). (d) Normalized electron density ne/nc (the color map is saturated to ne/nc = 0.3). (e) Mach number of the y component of the flow velocity, v⊥/cs.
    (a) and (b) Intensity profiles log(I[W/cm2]). (c) and (d) Power deposited in the plasma through inverse bremsstrahlung, SB (W/cm2). (e) 2.5D deflection rate dθSSD/dx (mrad/mm) as predicted by Hera. (a), (c), and (e) show the results predicted by the 2.5D beam bending rate [Eq. (24) with (S, β) = (1.7, 1)], while (b) and (d) show the results from the classical ray tracing scheme. The material boundaries are superimposed as black lines.
    Intensity profiles (W/cm2) of a 3D Gaussian laser pulse propagating through a flowing (M0 = 0.8) fully ionized carbon plasma at 10% to the critical density as predicted by 3D Hera simulations. (a) Intensity profile in the (x, y) plane, with the flow velocity along the y axis and the main laser direction along the x axis. (b) Intensity profile in the exit plane.
    Comparison between the fit of Eq. (D1) (dashed lines) and the exact calculations (solid lines) for different values of τSSD. The parameters in (a)–(c) correspond to a gold plasma (ZAu = 50, λmfp/f♯λ0 = 1.47) with γ0 = 0.007, 0.02, and 0.05, respectively, and those in (d) to a carbon plasma (ZC = 6, λmfp/f♯λ0 = 71) with γ0 = 0.05. Te = 3 keV and ne = 9 × 1026 m−3.
    • Table 1. Values of the fitting parameters S and β to be used in Eq. (19).

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      Table 1. Values of the fitting parameters S and β to be used in Eq. (19).

      Sβ
      3D TSSD ⊥vd1.72
      3D TSSD ⊥vd + PS0.83
      3D TSSD ‖vd1.71
      3D TSSD ‖vd + PS1.71
      3D LSSD60.8
    • Table 2. Polynomial coefficients an,m, bn,m, cn,m in Eqs. (D2)(D4).

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      Table 2. Polynomial coefficients an,m, bn,m, cn,m in Eqs. (D2)(D4).

      an,mm=0m=1m=2m=3m=4
      n=00.025 488−0.368 3221.224 227−0.549 2160.050 112
      n=10.001 769−0.043 2880.403 904−1.498 3380.667 592
      n=2−0.113 8531.603 793−5.426 9166.871 689−2.396 718
      n=30.189 056−2.603 4498.606 094−10.111 6743.370 095
      bn,mm=0m=1m=2m=3m=4
      n=0−0.007 6210.118 956−0.355 8690.163 3220.015 022
      n=1−0.088 6401.126 735−3.103 9823.160 460−1.086 508
      n=20.338 779−4.382 97912.275 832−12.029 223.862 822
      n=3−0.448 0775.745 170−16.150 0915.789 91−5.007 789
      cn,mm=0m=1m=2m=3m=4
      n=010.029 76−22.232 3826.037 80−14.192 602.822 304
      n=19.268 230−42.285 0270.621 96−45.765 9810.012 57
      n=2−373.594 71 539.699−2 128.1281 200.225−237.254 0
      n=34444.712−18 357.0125 459.51−14 404.952854.991
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    C. Ruyer, P. Loiseau, G. Riazuelo, R. Riquier, A. Debayle, P. E. Masson-Laborde, O. Morice. Accounting for speckle-scale beam bending in classical ray tracing schemes for propagating realistic pulses in indirect drive ignition conditions[J]. Matter and Radiation at Extremes, 2023, 8(2): 025901

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    Paper Information

    Category: Inertial Confinement Fusion Physics

    Received: Sep. 5, 2022

    Accepted: Dec. 24, 2022

    Published Online: Apr. 12, 2023

    The Author Email: Ruyer C. (charles.ruyer@cea.fr)

    DOI:10.1063/5.0124360

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