Suppression of the Rayleigh-Taylor Instability due to Self-Radiation in a Multiablation Target

A scheme to suppress the Rayleigh-Taylor instability has been investigated for a direct-drive inertial fusion target. In a high-$Z$ doped-plastic target, two ablation surfaces are formed separately—one driven by thermal radiation and the other driven by electron conduction. The growth of the Rayleigh-Taylor instability is significantly suppressed on the radiation-driven ablation surface inside the target due to the large ablation velocity and long density scale length. A significant reduction of the growth rate was observed in simulations and experiments using a brominated plastic target. A new direct-drive pellet was designed using this scheme.

Figure 1

1D simulated profiles of mass density (solid lines), electron temperature (dashed lines), and radiation brightness temperature (dash-dotted lines) in CHBr (a) and CH (b) targets at 1.2 ns after the onset of the main laser pulse. The origin of space is set to be the initial position of the target rear surface. RA and EA in (a) indicate radiation-driven ablation surface and electron-driven ablation surface, respectively.

Figure 2

2D simulated density contours of CHBr (a) and CH (b) targets at 1.9 ns after the beginning of the main laser pulse. The contour lines are drawn at isodensity of 40 levels increasing logarithmically from ${10}^{-2}$ to ${10}^1\mathrm{g}/{\mathrm{cm}}^3$.

Figure 3

Target trajectories observed in the experiment (circles) and simulation (solid gray line). The origins of time and space are set to be the onset of the main laser irradiation and the initial position of the rear surface of the target.

Figure 4

Face-on x-ray radiographs of laser driven perturbed CHBr (a) and CH (b) targets. (c) The temporal evolution of the areal density perturbation in CHBr (triangles) and CH (circles) targets. The origin of the time is set to be the time of onset of the main laser drive.

Figure 5

Pulse shape of the incident laser (a). 1D simulated profile of density (solid line) and pressure (dotted line) at 14 ns (b). Broken lines in (b) indicate interfaces of DT-CHBr and CHBr-CH.