Diagnosing and controlling mix in NIF implosion experiments

High mode number instability growth of ``isolated defects'' on the surfaces of NIF capsules can be large enough for the perturbation to penetrate the imploding shell and produce a jet of ablator material that enters the hot-spot. Since internal regions of the CH ablator are doped with Ge, mixing of this material into the hot-spot results in a clear signature of Ge K-shell emission. Evidence of jets entering the hot-spot has been recorded in x-ray images and spectra, consistent with simulation predictions.\footnote{B. A. Hammel, et al, High Energy Density Physics \textbf{- 6} (- 2) (2010). Prepared by LLNL under Contract DE-AC52-07NA27344.} Ignition targets have been designed to minimize instability growth, and capsule fabrication improvements are underway to reduce ``isolated defects.'' An experimental strategy has been developed where the final requirements for ignition targets can be adjusted through direct measurements of mix and experimental tuning.