Simulations of Diagnostic Emission due to Fuel-Pusher Mixing in Laser-Driven Implosions

It is important to develop diagnostics of the Rayleigh-Taylor instability that occurs during the deceleration phase of inertialconfinement-fusion capsule implosions because this instability is a crucial factor limiting the capsule performance.1 To simulate the effects of this instability and to assess possible diagnostic techniques, a mix model has been added to the one-dimensional (1-D) hydrocode LILAC.^ This model includes the effects of turbulent mixing on the hydrodynamic motion as well as on the temperature and material-concentration profiles within the plasma. In the work described here. this model is used to simulate time-resolved images of implosions of a gasfilled capsule that is representative of the kind proposed for near-term experiments on the 30-kJ, 60-beam OMEGA laser. In particular, the use of emission from thin chlorine-doped layers in the pusher is considered as ameans to track the growth of the mixed region near the fuel-pusher interface. It is shown how the onset of mix-induced emission varies over a series of polymer-shell targets that are identical, except that the additive layer is displaced by different amounts from the fuel-pusher interface in each target. It is also shown that the introduction of an additive layer sufficiently thick to produce adequate diagnostic emission has a minor effect on the implosion performance, compared with the effects of mix itself.