Radial structure of shell modulations near peak compression of spherical implosions

The structure of shell modulations is measured at peak compression of directly driven spherical implosions using absorption of titanium-doped layers placed at various distances of 1, 5, 7, and 9 μm from the inner surface of 20 μm thick plastic CH shells filled with 18 atm of D3He gas. The modulations are measured using the ratios of monochromatic core images taken inside and outside of the titanium 1s–2p absorption spectral region. Peak-compression, time-integrated areal-density modulations are higher at the inner shell surface, which is unstable during the deceleration phase of an implosion with a modulation level of 59±14%. The perturbations are lower in the central part of the shell, having a modulation level of 18±5%. The outer surface of the shell, which is unstable during the acceleration phase of an implosion, has a modulation level of 52±20%.