Inference of mix in direct-drive implosions on OMEGA

Abstract

Direct-drive implosions on the OMEGA laser [T. R. Boehly, D. L. Brown, R. S. Craxton et al., Opt. Commun. 133, 495 (1997)] have been diagnosed using a wide range of techniques based on neutrons, charged particles, and x rays. These implosions use full single-beam smoothing (distributed phase plates, 1-THz-bandwidth smoothing by spectral dispersion and polarization smoothing). The beam-to-beam power imbalance is ⩽5%. Fuel areal densities close to those in one-dimensional (1-D) simulations are inferred for implosions with calculated convergence ratios ∼15. The experimental neutron yields are ∼35% of 1-D yields. The complementary nature of the experimental observables is exploited to infer fuel shell mix in these implosions. Data suggest that this mix occurs at relatively small scales. Analysis of the experimental observables results in a picture of the core and mix region indicating that nearly 70% of the compressed fuel areal density is unmixed, and about 20% of the compressed shell areal density is in the mixed region. Comparisons of this model with inferred core conditions from argon-doped implosions are also presented.