Diagnosing ablator-fuel mix in NIF implosions using charged-particle spectrometry

Achieving areal-density and temperature conditions necessary for hot-spot ignition at the National Ignition Facility (NIF) requires careful control of four key implosion parameters, which characterize the expected performance. These are implosion velocity, fuel adiabat, hot-spot shape and ablator-fuel mix. It has been shown that these four parameters can be combined into an ignition threshold factor (ITF) that is a good predictor of implosion yield. In this talk, we present a new technique for diagnosing the extent of ablator-fuel mix. This technique, which utilizes compact Wedge-Range-Filter (WRF) spectrometers routinely used on NIF, relies on spectral measurements of elastically-scattered deuterons from the fuel, which should not have escaped the implosion without the presence of mix,. This work was supported in part by the U.S. DOE, LLNL and LLE.