Comprehensive Diagnosis of Growth Rates of the Ablative Rayleigh-Taylor Instability

The growth rate of the ablative Rayleigh-Taylor instability is approximated by $\gamma =\sqrt{kg/(1+kL)}-\beta k\dot{m}/{\rho }_a$, where $k$ is the perturbation wave number, $g$ the gravity, $L$ the density scale length, $\dot{m}$ the mass ablation rate, and ${\rho }_a$ the peak target density. The coefficient $\beta$ was evaluated for the first time by measuring all quantities of this formula except for $L$, which was taken from the simulation. Although the experimental value of $\beta =1.2\pm 0.7$ at short perturbation wavelengths is in reasonably good agreement with the theoretical prediction of $\beta =1.7$, it is found to be larger than the prediction at long wavelengths.

Figure 1

The schematic view of the measurements of all quantities of Eq. (1).

Figure 2

(a) The raw images of the Rayleigh-Taylor experiment for the perturbation wavelength of $20\mu \mathrm{m}$. The time evolution of the growth factor for (b) $\lambda =20\mu \mathrm{m}$ and (c) $\lambda =50\mu \mathrm{m}$.

Figure 3

(a) The raw image of the target trajectory measured with an x-ray streak camera. (b) The target trajectory as a function of time.

Figure 4

(a) The raw image of the mass ablation rate measurement. (b) The time development of the transmittance.