Diagnosis of pusher‐fuel mixing for high growth‐factor implosions (abstract)a)

The degradation in implosion performance of surface‐pitted, indirectly driven Br‐doped capsules which have been intentionally designed to be susceptible to large hydrodynamic instability growth has been systematically and reproducibly measured by a wide array of x‐ray and neutron diagnostics. Primary and secondary neutron yields, and x‐ray line ratios and durations from Ar and Ti fuel and pusher dopants are presented, showing clear sensitivity to increasing surface roughness and by inference, increasing pusher‐fuel mix. The sensitivity of core x‐ray emissivity and neutron bang‐times to micron variations in capsule ablator thickness is also demonstrated. The experimental trends are compared to expectations based on two different models for the effects of instability growth at the pusher‐fuel interface (atomic mixing versus Rayleigh–Taylor bubble‐and‐spike growth).