Viscous effects in ICF target implosions

Using the implicit/hybrid Eulerian simulation code ePLAS
^1,2
, we study the effects of viscous modeling choices on the predicted implosive behavior of ICF targets as employed on the NIF. Results from traditional artificial viscosity and real viscosity are compared in both planar and 2D cylindrical geometry. We examine the implosion of spherical and slightly ellipsoidal DT shells containing dense DT gas in ~20 - 50 micron “voids.” Before implosion the shells have been shock compressed to ~10
²
to 10
³
g/cm
³
densities, and 0.3 to 1.2 keV temperatures. Effects from real viscosity are largely independent of density, but can work to smear shocks over some 20 microns when the ion temperature approaches 1.0 keV. Artificial viscosity sets shocks of all strength to ~3 × the local cell widths.