Update on Thermal and Hydrodynamic Simulations on LMJ Cryogenic Targets

The temperature of the cryogenic target inside the hohlraum has been studied with a computational fluid dynamics code (FLUENT). Specific models have been developed and used for both thermal and hydrodynamic calculations.

With thermal calculations only, we first have found the optimum heat flux required to counteract the effect of the laser entrance windows. This heat flux is centered on the hohlraum wall along the axis of revolution. With this heat flux, the temperature surface profiles of the capsule and the DT ice layer have been significantly reduced. Second, the sensitivity of the target temperature profiles (capsule and DT layer) relatively to capsule displacement has been determined. Thirdly, the effect of the shield extraction (shield surrounding the cryogenic structure) has been studied and has indicated that the target lifetime before the laser shot is less than 1s. Meanwhile, with hydrodynamic simulations, we have investigated the surface temperature profiles alteration due to He and H₂ mixture convection within the hohlraum.

In order to find out the variations between different configurations, results of these studies are given with seven significant digit outputs. Those results only indicate a trend because of the material's properties incertitude and the code approximation.