Radiographic measurement of high-pressure, gas-filled pore collapse due to preheat*

The Marble experiments on NIF explored the degree of mixing between a porous foam and a gas fill as a function of pore size, but initial measurements displayed an unexpected insensitivity to pore size. It was hypothesized that the pores were collapsing due to preheat, which destroyed the initial porosity condition, and therefore a high-Z gas fill was introduced so that the additional electron pressure would support the pores against collapse. We conducted a separate set of experiments on Omega-60 to explore this pore collapse in greater detail by radiographically measuring the size of a macro-pore in a shock tube filled with a 6 atm high-Z gas mix. We compare the collapse of the macro-pore for two conditions: one with a pure Krypton gas fill and the other with a Krypton/Hydrogen mix, where we expect the latter case to have a lower pressure and to result in a more compressed macro-pore. LA-UR-23-27433