Preheat Effect on MARBLE Foams

Recent experimental results from the MARBLE campaign at NIF shows that the initial size of macro-pore foam has no significant effect on the behavior of mix. The results suggest that the initial size of macro-pore foam may be disrupted by preheat from the hohlraum x-ray. The foam may expand due to the preheat, which results in decrease in the macro-pore size. Quantifying the amount of preheat will reduce uncertainty in MARBLE macro-pore simulations. Two types of preheat platforms were developed at Omega laser facility to provide data to guide NIF preheat simulation: the first study is to measure the aluminum expansion rates from a direct-drive laser condition, the second study is to measure the plastic expansion rates from an indirect-drive hohlraum x-ray. The amount of preheat will be quantified using radiographic x-ray images and a radiation-hydrodynamic code.