Superfluid avalanches

Avalanches are seen in the invasion percolation region of an adsorption/desorption isotherm for superfluid super(4)He on a Nuclepore filter. A theory of these avalanches combines elements from the geometry of the pore space of Nuclepore and elements from the dynamics of superfluid films. The geometry of Nuclepore filters is studied and the percolation properties of these systems are assessed. The percolation threshold is found to be characterized by the average coordination number of the pores. A model of the coupled pore space/superfluid system is introduced. This model is studied numerically and is shown to lead to self-quenched avalanches that share many qualitative properties with the avalanches seen in experiment.