Avalanche behavior in the draining of superfluid helium from the porous material Nuclepore - art. no. 024516

Examination of the primary draining curve in studies of the capillary conde nsation of He-4 in the porous material Nuclepore reveals that lowering the chemical potential when the helium is in the superfluid state causes the Nu clepore pore spaces to drain in a series of large-scale avalanches in which substantial numbers of pores (up to similar to2.5% of the sample) drain as a single cooperative event, i.e.. as an avalanche. In this work we documen t the behavior of such avalanches in this porous material for two character istic diameter pore sizes 700 nm and 30 nm. We examine the relevance of var ious theoretical models which one might apply to the system and conclude th at none is completely satisfactory.