Shell Mix in the Compressed Core of Spherical Implosions

The Rayleigh-Taylor instability in its highly nonlinear, turbulent stage causes atomic-scale mixing of the shell material with the fuel in the compressed core of inertial-confinement fusion targets. The density of shell material mixed into the outer core of direct-drive plastic-shell spherical-target implosions on the 60-beam, OMEGA laser system is estimated to be 3.4(±1.2) g/cm³ from time-resolved x-ray spectroscopy, charged-particle spectroscopy, and core x-ray images. The estimated fuel density, 3.6(±1) g/cm³, accounts for only ~50% of the neutron-burn-averaged electron density, nₑ=2.2(±0.4)×10²⁴ cm^-3.