Nonlinear kinetic estimate of Raman reflectivity in a hohlraum plasma with a radiation hydrodynamics code

In this Letter, we introduce an inline model for stimulated Raman scattering (SRS), which runs on our radiation hydrodynamics code troll. This model accounts for nonlinear kinetic effects and for the SRS feedback on the plasma hydrodynamics. We dubbed it PIEM because it is a fully “PredIctivE Model,” because no free parameter is to be adjusted a posteriori in order to match the experimental results. PIEM predictions are compared against experimental measurements performed at the Ligne d'Intégration Laser. From these comparisons, we discuss the PIEM ability to correctly catch the impact of nonlinear kinetic effects on SRS.

Figure 1

(a) Incident laser power used in the 2011 campaign (red solid line) and in the 2013 campaign (black dashed line). (b) SRS reflected power measured in the 2011 campaign (red solid line) and in the 2013 campaign (black dashed line). The reflectivity decreases later in the 2011 campaign due to a later decrease of the incident power.

Figure 2

SRS-reflected spectrum (a) as measured experimentally and (b) as predicted by PIEM in arbitrary units. In both figures, the black stars and the horizontal lines indicate, respectively, the wavelengths at maximum and the widths of the experimental spectrum. The PIEM spectrum in (a) was designed so as to assume time-independent maxima, which is in contrast with the experimental spectrum in (b).

Figure 3

SRS reflected power as measured experimentally (blue curve with pluses), as predicted by PIEM (red solid line), and by a linear model (green dashed-dotted line). The black dashed line is the incident laser power divided by 5.

Figure 4

Transmitted power as derived numerically (red solid line) and as measured experimentally (blue solid line with pluses).

Figure 5

Time evolution of $k_p{\lambda }_D$ (black dashed line) and of ${\nu }_L/{\omega }_{pe}$ (green solid line) as calculated by PIEM.