Measuring the principle Hugoniot of ICF-relevant TMPTA foam

Wetted-foam layers are of significant interest for ICF capsules, due to the unprecedented control they provide over the convergence ratio of the implosion, and the opportunity this affords to minimize hydrodynamic instability growth. However, the equation of state (EOS) for fusion relevant foams is not well characterized, and many simulations therefore rely on modelling such foams as a homogeneous medium of the foam average density. The accuracy of this hypothesis is not known with great confidence. To address this question, an experiment was performed in January 2022 using the VULCAN Laser at the Central Laser Facility. The aim was to measure the EOS of TMPTA foams at 260 mg/cc, corresponding to the density of DT-wetted-foam layers relevant to ICF research. Such a foam would be also be directly relevant for recently proposed ‘hydrodynamic equivalent’ capsules. VISAR was used to measure the shock velocity of both the foam and a quartz reference layer, while streaked optical pyrometry was used to measure the temperature of the shocked material. Preliminary results suggest that, for the 20 – 120 GPa pressure range accessed, this material can indeed be well described using the equation of state of the homogeneous medium at the foam density.