Counterpropagating Radiative Shock Experiments on the Orion Laser

We present new experiments to study the formation of radiative shocks and the interaction between two counterpropagating radiative shocks. The experiments are performed at the Orion laser facility, which is used to drive shocks in xenon inside large aspect ratio gas cells. The collision between the two shocks and their respective radiative precursors, combined with the formation of inherently three-dimensional shocks, provides a novel platform particularly suited for the benchmarking of numerical codes. The dynamics of the shocks before and after the collision are investigated using point-projection x-ray backlighting while, simultaneously, the electron density in the radiative precursor was measured via optical laser interferometry. Modeling of the experiments using the 2D radiation hydrodynamic codes nym and petra shows very good agreement with the experimental results.

Figure 1

Octogonal gas cells (nominal dimensions in mm). (a) 3D rendering. (b) Side-on, cut view. (c) Face-on view and diagnostics.

Figure 2

Counterpropagating shock dynamics at different times from (a)–(c) experimental x-ray backlighting and (d)–(f) 2D numerical simulations. Each simulation image shows mass density (top half, log scale), electron temperature (bottom-left quadrant, linear scale) and materials (bottom-right quadrant). The color bar used to represent mass density in (d) also displays linear values of electron temperature in the ranges (d) 0–35 eV, (e) 0–60 eV, and (f) 0–40 eV.

Figure 3

Electron density measurements in the radiative precursors. (a),(b) 1D axial streak interferometry results with respect to (a) the raw data and (b) the analysis of (a), resulting in the line electron density $n_{e}L$ ($\times 10^{18}{\mathrm{cm}}^{-2}$) as a function of time. The dashed lines in (a) mark values of $n_{e}L\sim 1.5\times 10^{18}{\mathrm{cm}}^{-2}$. (c),(d) 2D GOI results at 18 ns. The top half of (c) shows raw data, and the bottom half a preshot interferogram. (d) 2D $n_{e}L$ map from an analysis of (c). (e) Axial profiles of $n_{e}L$ at 18, 20, 22, and 24 ns from (b) and (d). Also shown are $n_{e}L$ profiles at 18 ns off axis [the positions marked $A$ and $B$ in (d)]. (f) Simulated axial profiles of $n_{e}L$ at 14, 16, 18, and 20 ns.

Figure 4

Axial profiles of mass density ($\rho$), electron density ($n_e$), electron temperature ($T_e$), and radiation temperature ($T_R$) from 2D simulations of counterpropagating radiative shocks at: (a) 22 ns [before the collision; see Fig. 3], (b) 30 ns (shortly after the collision, note the change in the $X$ and $Y$ scales), (c) 36 ns [after the collision; see Fig. 3]. The axial distance is taken from the center of the diagnostic window, which marks the position of a reflective boundary used for the simulations.