Preheat and ablation broadening due to nonthermal electron energy transport for Z>1.

Over the past few years, the NRL theory group has presented and published a variety of theoretical works on the effect of nonlocal electron energy transport on fuel preheat and ablation layer broadening in direct drive laser fusion targets.  The goal is not an exact model arrived at by say a Monte Carlo simulation, but rather a model accurate enough and simple enough that it can be utilized at each time step of a fluid simulation.  These works involved both Krook models and a combination of Krook and Fokker Planck (FP) models.  The latter works used the Krook model to determine the nonlocal energy flux at its maximum point (within a mfp or so their formation) and an approximate FP model to determine their deposition.  A characteristic of the FP model is that it predicts orders of magnitude less fuel preheat than Krook models; after many mfp’s the Krook and FP models behave very differently.  Earlier publications treated planar and spherical cases for Z=1.  This work extends the theory to include Z > 1 ablators.  Unlike the diffusion model, which simply has a diffusion coefficient going as 1/Z, a more accurate FP model does not have such a simple coupling of Z to single spatial equation, but has the Z only in the velocity terms, and not in the spatial terms.  However, the solution of this more complex equation does show a decreasing fuel preheat with an increase in Z.