Probing the internal structure of nuclepore with hysteretic capillary condensation - art. no. 174503

We report filling (adsorption) and draining (desorption) measurements of su perfluid He-4 in the porous material nuclepore. These low-temperature measu rements explore the classical hysteretic properties of the capillary conden sation of the liquid, while utilizing the propagation of third sound in the superfluid helium as an in situ probe of the chemical potential. We presen t measurements of global hysteresis loops, subloops, and reversal curves. W ith this data, we determine that the interconnected pore structure of the m aterial is critical to the draining process. In addition, we present measur ements of the connectivity and pore size distributions for nuclepore, and c ompare these results to calculations and earlier measurements. This work es tablishes the utility of the novel working fluid superfluid He-4 and the ap plicability of the techniques used here for such studies of porous material s.