Saturation of perturbation growth in ablatively driven planar laser targets

Saturation of the mass variation growth during the shock transit time, theoretically predicted for the surface roughness case by Ishizaki and Nishihara [Phys. Rev. Lett. 78, 1920 (1997)] and for the laser imprint case by Taylor et al. [Phys. Rev. Lett. 79, 1861 (1997)], is studied analytically and numerically. The saturation is demonstrated to be essentially the same effect in both cases, caused by the stabilizing action of mass ablation. Scalings of saturation time and saturation level for the two cases are related. For lower-density foam targets, the peak level of mass variation is proportional approximately to ρ 0 1/2 and exactly to ρ 0 for the cases of laser imprint and surface roughness, respectively.