Hydrodynamic growth of shell modulations in the deceleration phase of spherical direct-drive implosions

Abstract

The evolution of shell modulations was measured in targets with titanium-doped layers using differential imaging [B. Yaakobi et al., Phys. Plasmas 7, 3727 (2000)] near peak compression of direct-drive spherical implosions. Inner-shell modulations grow throughout the deceleration phase of the implosion due to the Rayleigh–Taylor instability with relative modulation levels of ∼20% at peak neutron production and ∼50% at peak compression (∼100 ps later) in targets with 1-mm-diam, 20-μm-thick shells filled with 4 atm of D3He gas. In addition, the shell modulations grow up to about 1.5 times due to Bell–Plesset convergent effects during the same period. At peak compression the inner part of the shell has a higher modulation level than other parts of the shell.